check on twopc enabled flag for unresolved transactions call

Signed-off-by: Harshit Gangal <harshit@planetscale.com>

go/vt/vttablet/tabletserver/dt_executor.go

@@ -359,5 +359,8 @@ func (dte *DTExecutor) inTransaction(f func(*StatefulConnection) error) error {
 
 // UnresolvedTransactions returns the list of unresolved distributed transactions.
 func (dte *DTExecutor) UnresolvedTransactions() ([]*querypb.TransactionMetadata, error) {
+	if !dte.te.twopcEnabled {
+		return nil, vterrors.Errorf(vtrpcpb.Code_INVALID_ARGUMENT, "2pc is not enabled")
+	}
 	return dte.te.twoPC.UnresolvedTransactions(dte.ctx, time.Now().Add(-dte.te.abandonAge))
 }

go/vt/vttablet/tabletserver/dt_executor_test.go

@@ -654,6 +654,12 @@ func TestNoTwopc(t *testing.T) {
 			_, _, _, err := txe.ReadTwopcInflight()
 			return err
 		},
+	}, {
+		desc: "ReadUnresolvedTransactions",
+		fun: func() error {
+			_, err := txe.UnresolvedTransactions()
+			return err
+		},
 	}}
 
 	want := "2pc is not enabled"