Delete individual volume snapshots as part of the group snapshot delete API and prevent users from deleting individual volume snapshots if it is part of an existing group snapshot

Also revert commit bb29899ca3.

pkg/snapshotter/snapshotter_test.go

@@ -468,7 +468,7 @@ func TestGetSnapshotStatus(t *testing.T) {
 		}
 
 		s := NewSnapshotter(csiConn)
-		ready, createTime, size, err := s.GetSnapshotStatus(context.Background(), test.snapshotID, test.snapshotterListCredentials)
+		ready, createTime, size, _, err := s.GetSnapshotStatus(context.Background(), test.snapshotID, test.snapshotterListCredentials)
 		if test.expectError && err == nil {
 			t.Errorf("test %q: Expected error, got none", test.name)
 		}