Skip adding NEGs in to-be-deleted state when querying from Svcneg.

* Backend Service updates are performed by providing a new list of
  backends every time. Thus, if we skip adding NEGs in to-be-delated
  state, they will be detached from Backend Services when a sync
  triggers.
* Currently, in fail-safe situation we get NEGs by querying GCE. Once
  CRD is ready, we will make sure to get the subnet information and also
  include NEGs from non-default subnet.

pkg/backends/neg_linker.go

@@ -265,6 +265,9 @@ func getNegUrlsFromSvcneg(key string, svcNegLister cache.Indexer, logger klog.Lo
 	svcneg := obj.(*negv1beta1.ServiceNetworkEndpointGroup)
 
 	for _, negRef := range svcneg.Status.NetworkEndpointGroups {
+		if flags.F.EnableMultiSubnetClusterPhase1 && negRef.State == negv1beta1.ToBeDeletedState {
+			continue
+		}
 		negUrls = append(negUrls, negRef.SelfLink)
 	}
 	return negUrls, true

pkg/backends/neg_linker_test.go

@@ -206,6 +206,7 @@ func TestLinkBackendServiceToNEG(t *testing.T) {
 
 func TestGetNegSelfLinks(t *testing.T) {
 	t.Parallel()
+	flags.F.EnableMultiSubnetClusterPhase1 = true
 
 	groupKeys := []GroupKey{{Zone: testZone1}, {Zone: testZone2}}
 	namespace, svcName, port := "ns", "name", "port"
@@ -268,6 +269,17 @@ func TestGetNegSelfLinks(t *testing.T) {
 			},
 			expectedNegCount: 4,
 		},
+		{
+			desc:           "Get NEGs from SvcNeg, all NEGs are in active state, and containing NEGs from non-default subnet",
+			populateSvcNeg: true,
+			testNegRef: []v1beta1.NegObjectReference{
+				createNegRef(testZone1, defaultSubnetNegName, v1beta1.ActiveState),
+				createNegRef(testZone1, nonDefaultSubnetNegName, v1beta1.ToBeDeletedState),
+				createNegRef(testZone2, defaultSubnetNegName, v1beta1.ActiveState),
+				createNegRef(testZone2, nonDefaultSubnetNegName, v1beta1.ToBeDeletedState),
+			},
+			expectedNegCount: 2,
+		},
 		{
 			desc:             "Get NEGs from GCE",
 			populateSvcNeg:   false,