Remove PG-14 rebase artifact from dblink and fix for dblink_get_conn (#1484)

* Remove PG-14 rebase artifact from dblink.

dblink_connstr_check changed its return type as part of 9b75844.
It is error-prone to rebase dblink sources since then.
There is no need for second dblink_connstr_check, even thought it
produces no harm.

Double-check from gpdb-7:
https://github.com/greenplum-db/gpdb-archive/blob/main/contrib/dblink/dblink.c#L290

Found during PG-16 rebase review.

* Fix DBLINK_GET_CONN

https://github.com/apache/cloudberry/blob/9b758447dfb65dcb8024f2465c410221ded12841/contrib/dblink/dblink.c#L185


use modified conn_str in dblink_get_conn, check out 8420c0f commit msg

https://github.com/apache/cloudberry/blob/9b758447dfb65dcb8024f2465c410221ded12841/contrib/dblink/dblink.c#L185-L195

Author: reshke

contrib/dblink/dblink.c

@@ -198,7 +198,7 @@ dblink_get_conn(char *conname_or_str,
 		connstr = get_connect_string(conname_or_str);
 		if (connstr == NULL)
 			connstr = conname_or_str;
-		dblink_connstr_check(connstr);
+		connstr = dblink_connstr_check(connstr);
 
 		/*
 		 * We must obey fd.c's limit on non-virtual file descriptors.  Assume
@@ -312,7 +312,6 @@ dblink_connect(PG_FUNCTION_ARGS)
 
 	/* check password in connection string if not superuser */
 	connstr = dblink_connstr_check(connstr);
-	dblink_connstr_check(connstr);
 
 	/*
 	 * We must obey fd.c's limit on non-virtual file descriptors.  Assume that