Plug memory leak

Commit 054325c created a memory leak in PQsendQueryInternal in case
an error occurs while sending the message.  Repair.

Backpatch to 14, like that commit.  Reported by Coverity.

Author: alvherre

src/interfaces/libpq/fe-exec.c

@@ -1542,6 +1542,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 
 sendFailed:
 	pqRecycleCmdQueueEntry(conn, entry);
+	pqRecycleCmdQueueEntry(conn, entry2);
 	/* error message should be set up already */
 	return 0;
 }