Instantiate the rcsw with gatewayAlive=true (#8590) (#8725) (#8787)

If we don't instantiate the RemoteClusterWatcher with gatewayAlive=true, then
there will be a small period all services will fail-fast unexpectedly.

Simply Instantiate the RemoteClusterWatcher with gatewayAlive=true.

Signed-off-by: Ao Chen <chenao3220@gmail.com>

multicluster/service-mirror/cluster_watcher.go

@@ -195,6 +195,8 @@ func NewRemoteClusterServiceWatcher(
 		repairPeriod:            repairPeriod,
 		liveness:                liveness,
 		headlessServicesEnabled: enableHeadlessSvc,
+		// always instantiate the gatewayAlive=true to prevent unexpected service fail fast
+		gatewayAlive: true,
 	}, nil
 }