Test fixes:

- For reconnection/and multi host tests specify also socket location,
since mtr doesn't use default socket for localhost connections

- parse_connection_string now returns NULL for empty password in
  curly braces

libmariadb/mariadb_lib.c

@@ -841,6 +841,7 @@ static int parse_connection_string(MYSQL *mysql, const char *unused __attribute_
           {
             pos++;
             val= pos;
+            continue;
           }
         }
         break;