Avoid races in connect.test.

The problem was in a test case for Bug33507:
  - when the number of active connections reaches the limit,
    the server accepts only root connections. That's achieved by
    accepting a connection, negotiating with the client and
    checking user credentials. If it is not SUPER, the connection
    is dropped.
  - when the server accepts connection, it increases the counter;
  - when the server drops connection, it decreases the counter;
  - the race was in between of decreasing the counter and accepting
    new connection:
    - max_user_connections = 2;
    - 2 oridinary user connections accepted;
    - extra user connection is establishing;
    - server checked user credentials, and sent 'Too many connections'
      error;
    - the client receives the error and establishes extra SUPER user
      connection;
    - the server however didn't decrease the counter (the extra
      user connection still is "alive" in the server) -- so, the new
      SUPER-user connection, will be dropped, because it exceeds
      (max_user_connections + 1).

The fix is to implement "safe connect", which makes several attempts
to connect and use it in the test script.


mysql-test/r/connect.result:
  Update test file.
mysql-test/t/connect.test:
  Avoid races in connect.test.
mysql-test/include/connect2.inc:
  Auxiliary routine to establish a connection reliably.

mysql-test/t/connect.test

@@ -114,106 +114,94 @@ drop table t1;
 --echo # -- End of 4.1 tests
 --echo # ------------------------------------------------------------------
 
+###########################################################################
+
 --echo
 --echo # -- Bug#33507: Event scheduler creates more threads than max_connections
 --echo # -- which results in user lockout.
---echo
 
+--echo
 GRANT USAGE ON *.* TO mysqltest_u1@localhost;
 
 # NOTE: if the test case fails sporadically due to spurious connections,
 # consider disabling all users.
 
 --echo
-
 let $saved_max_connections = `SELECT @@global.max_connections`;
-
 SET GLOBAL max_connections = 3;
 SET GLOBAL event_scheduler = ON;
 
 --echo
---echo # -- Waiting for old connections to close...
-let $wait_condition =
-  SELECT COUNT(*) = 1
-  FROM information_schema.processlist
-  WHERE db = 'test';
---source include/wait_condition.inc
-
---echo
+--echo # -- Waiting for Event Scheduler to start...
 let $wait_condition =
   SELECT COUNT(*) = 1
   FROM information_schema.processlist
   WHERE user = 'event_scheduler';
 --source include/wait_condition.inc
---echo
 
+--echo
 --echo # -- Disconnecting default connection...
 --disconnect default
 
 --echo
 --echo # -- Check that we allow exactly three user connections, no matter how
 --echo # -- many threads are running.
+
 --echo 
-
 --echo # -- Connecting (1)...
---connect (con_1,localhost,mysqltest_u1)
+let $con_name = con_1;
+let $con_user_name = mysqltest_u1;
+--source include/connect2.inc
 
 --echo
---echo # -- Waiting for root connection to close...
-let $wait_condition =
-  SELECT COUNT(*) = 1
-  FROM information_schema.processlist
-  WHERE db = 'test';
---source include/wait_condition.inc
---echo
-
 --echo # -- Connecting (2)...
---connect (con_2,localhost,mysqltest_u1)
-
---echo # -- Connecting (3)...
---connect (con_3,localhost,mysqltest_u1)
-
---echo # -- Connecting (4)...
---disable_query_log
---error ER_CON_COUNT_ERROR
---connect (con_4,localhost,mysqltest_u1)
---enable_query_log
+let $con_name = con_2;
+let $con_user_name = mysqltest_u1;
+--source include/connect2.inc
 
 --echo
---echo # -- Waiting for the last connection to close...
-let $wait_condition =
-  SELECT COUNT(*) = 3
-  FROM information_schema.processlist
-  WHERE db = 'test';
---source include/wait_condition.inc
+--echo # -- Connecting (3)...
+let $con_name = con_3;
+let $con_user_name = mysqltest_u1;
+--source include/connect2.inc
+
+--echo
+--echo # -- Connecting (4) [should fail]...
+let $con_name = con_4;
+let $con_user_name = mysqltest_u1;
+let $wait_timeout = 5;
+--source include/connect2.inc
 
 --echo
 --echo # -- Check that we allow one extra SUPER-user connection.
---echo
 
+--echo
 --echo # -- Connecting super (1)...
---connect (con_super_1,localhost,root)
-
---echo # -- Connecting super (2)...
---disable_query_log
---error ER_CON_COUNT_ERROR
---connect (con_super_2,localhost,root)
---enable_query_log
+let $con_name = con_super_1;
+let $con_user_name = root;
+--source include/connect2.inc
 
 --echo
-# Ensure that we have Event Scheduler thread, 3 ordinary user connections and
-# one extra super-user connection.
+--echo # -- Connecting super (2) [should fail]...
+let $con_name = con_super_2;
+let $con_user_name = root;
+let $wait_timeout = 5;
+--source include/connect2.inc
+
+--echo
+--echo # -- Ensure that we have Event Scheduler thread, 3 ordinary user
+--echo # -- connections and one extra super-user connection.
 SELECT user FROM information_schema.processlist ORDER BY id;
 
 --echo
 --echo # -- Resetting variables...
-
 --eval SET GLOBAL max_connections = $saved_max_connections
 
 --echo
 --echo # -- Stopping Event Scheduler...
 SET GLOBAL event_scheduler = OFF;
 
+--echo
 --echo # -- Waiting for Event Scheduler to stop...
 let $wait_condition =
   SELECT COUNT(*) = 0