Don't hardcode contrib_regression dbname in postgres_fdw and dblink tests.

That allows parallel installcheck to succeed inside contrib/. The
output is not particularly pretty unless make's -O option to
synchronize the output is used.

There's other tests, outside contrib, that use a hardcoded,
non-unique, database name. Those prohibit paralell installcheck to be
used across more directories; but that's something for a separate
patch.

contrib/dblink/expected/dblink.out

@@ -88,9 +88,12 @@ SELECT dblink_build_sql_delete('"MySchema"."Foo"','1 2',2,'{"0", "a"}');
  DELETE FROM "MySchema"."Foo" WHERE f1 = '0' AND f2 = 'a'
 (1 row)
 
+CREATE FUNCTION connection_parameters() RETURNS text LANGUAGE SQL AS $f$
+       SELECT $$dbname='$$||current_database()||$$'$$;
+$f$;
 -- regular old dblink
 SELECT *
-FROM dblink('dbname=contrib_regression','SELECT * FROM foo') AS t(a int, b text, c text[])
+FROM dblink(connection_parameters(),'SELECT * FROM foo') AS t(a int, b text, c text[])
 WHERE t.a > 7;
  a | b |     c      
 ---+---+------------
@@ -116,9 +119,9 @@ DECLARE
 	detail text;
 BEGIN
 	PERFORM wait_pid(crash_pid)
-	FROM dblink('dbname=contrib_regression', $$
+	FROM dblink(connection_parameters(), $$
 		SELECT pg_backend_pid() FROM dblink(
-			'service=test_ldap dbname=contrib_regression',
+			'service=test_ldap '||connection_parameters(),
 			-- This string concatenation is a hack to shoehorn a
 			-- set_pgservicefile call into the SQL statement.
 			'SELECT 1' || set_pgservicefile('pg_service.conf')
@@ -131,7 +134,7 @@ EXCEPTION WHEN OTHERS THEN
 END
 $pl$;
 -- create a persistent connection
-SELECT dblink_connect('dbname=contrib_regression');
+SELECT dblink_connect(connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -267,14 +270,14 @@ WHERE t.a > 7;
 ERROR:  connection not available
 -- put more data into our slave table, first using arbitrary connection syntax
 -- but truncate the actual return value so we can use diff to check for success
-SELECT substr(dblink_exec('dbname=contrib_regression','INSERT INTO foo VALUES(10,''k'',''{"a10","b10","c10"}'')'),1,6);
+SELECT substr(dblink_exec(connection_parameters(),'INSERT INTO foo VALUES(10,''k'',''{"a10","b10","c10"}'')'),1,6);
  substr 
 --------
  INSERT
 (1 row)
 
 -- create a persistent connection
-SELECT dblink_connect('dbname=contrib_regression');
+SELECT dblink_connect(connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -374,7 +377,7 @@ ERROR:  could not establish connection
 DETAIL:  missing "=" after "myconn" in connection info string
 
 -- create a named persistent connection
-SELECT dblink_connect('myconn','dbname=contrib_regression');
+SELECT dblink_connect('myconn',connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -403,10 +406,10 @@ CONTEXT:  Error occurred on dblink connection named "myconn": could not execute
 
 -- create a second named persistent connection
 -- should error with "duplicate connection name"
-SELECT dblink_connect('myconn','dbname=contrib_regression');
+SELECT dblink_connect('myconn',connection_parameters());
 ERROR:  duplicate connection name
 -- create a second named persistent connection with a new name
-SELECT dblink_connect('myconn2','dbname=contrib_regression');
+SELECT dblink_connect('myconn2',connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -601,7 +604,7 @@ ERROR:  could not establish connection
 DETAIL:  missing "=" after "myconn" in connection info string
 
 -- create a named persistent connection
-SELECT dblink_connect('myconn','dbname=contrib_regression');
+SELECT dblink_connect('myconn',connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -677,7 +680,7 @@ SELECT dblink_disconnect('myconn');
 SELECT dblink_disconnect('myconn');
 ERROR:  connection "myconn" not available
 -- test asynchronous queries
-SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
+SELECT dblink_connect('dtest1', connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -690,7 +693,7 @@ SELECT * from
   1
 (1 row)
 
-SELECT dblink_connect('dtest2', 'dbname=contrib_regression');
+SELECT dblink_connect('dtest2', connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -703,7 +706,7 @@ SELECT * from
   1
 (1 row)
 
-SELECT dblink_connect('dtest3', 'dbname=contrib_regression');
+SELECT dblink_connect('dtest3', connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -777,7 +780,7 @@ SELECT * from result;
  10 | k  | {a10,b10,c10}
 (11 rows)
 
-SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
+SELECT dblink_connect('dtest1', connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -810,8 +813,12 @@ SELECT dblink_disconnect('dtest1');
 
 -- test foreign data wrapper functionality
 CREATE ROLE dblink_regression_test;
-CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw
-  OPTIONS (dbname 'contrib_regression');
+DO $d$
+    BEGIN
+        EXECUTE $$CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw
+            OPTIONS (dbname '$$||current_database()||$$')$$;
+    END;
+$d$;
 CREATE USER MAPPING FOR public SERVER fdtest
   OPTIONS (server 'localhost');  -- fail, can't specify server here
 ERROR:  invalid option "server"
@@ -854,7 +861,7 @@ DROP USER dblink_regression_test;
 DROP USER MAPPING FOR public SERVER fdtest;
 DROP SERVER fdtest;
 -- test asynchronous notifications
-SELECT dblink_connect('dbname=contrib_regression');
+SELECT dblink_connect(connection_parameters());
  dblink_connect 
 ----------------
  OK
@@ -943,7 +950,7 @@ SELECT dblink_build_sql_delete('test_dropped', '1', 1,
 SET datestyle = ISO, MDY;
 SET intervalstyle = postgres;
 SET timezone = UTC;
-SELECT dblink_connect('myconn','dbname=contrib_regression');
+SELECT dblink_connect('myconn',connection_parameters());
  dblink_connect 
 ----------------
  OK