sync to head (istio#4709)

Automatic merge from submit-queue.

Turn on Istio-ca grpc service by default

TODO(wattli): remove the duplicate flags in bin/ and install/

security/cmd/istio_ca/main.go

@@ -178,8 +178,8 @@ func init() {
 		defaultWorkloadMinCertGracePeriod, "The minimum workload certificate rotation grace period.")
 
 	// gRPC server for signing CSRs.
-	flags.StringVar(&opts.grpcHostname, "grpc-hostname", "localhost", "The hostname for GRPC server.")
-	flags.IntVar(&opts.grpcPort, "grpc-port", 0, "The port number for GRPC server. "+
+	flags.StringVar(&opts.grpcHostname, "grpc-hostname", "istio-ca", "The hostname for GRPC server.")
+	flags.IntVar(&opts.grpcPort, "grpc-port", 8060, "The port number for GRPC server. "+
 		"If unspecified, Istio CA will not server GRPC request.")
 
 	// Upstream CA configuration