[release-21.0] Online DDL: fix defer function, potential connection p…

…ool exhaustion (#17207) (#17210)

Signed-off-by: Shlomi Noach <[email protected]>
Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

go/vt/vttablet/onlineddl/executor.go

@@ -963,13 +963,13 @@ func (e *Executor) cutOverVReplMigration(ctx context.Context, s *VReplStream, sh
 	if err != nil {
 		return err
 	}
+	defer lockConn.Recycle()
 	// Set large enough `@@lock_wait_timeout` so that it does not interfere with the cut-over operation.
 	// The code will ensure everything that needs to be terminated by `migrationCutOverThreshold` will be terminated.
 	lockConnRestoreLockWaitTimeout, err := e.initConnectionLockWaitTimeout(ctx, lockConn.Conn, 5*migrationCutOverThreshold)
 	if err != nil {
 		return err
 	}
-	defer lockConn.Recycle()
 	defer lockConnRestoreLockWaitTimeout()
 	defer lockConn.Conn.Exec(ctx, sqlUnlockTables, 1, false)