Use different NATS servers for federation tests.

Otherwise it would be possible to send events to remote sessions (through
NATS) even if they are connected to a separate signaling server which has
it's own NATS server in reality.

hub_test.go

@@ -196,11 +196,17 @@ func CreateClusteredHubsForTestWithConfig(t *testing.T, getConfigFunc func(*http
 		server2.Close()
 	})
 
-	nats := startLocalNatsServer(t)
+	nats1 := startLocalNatsServer(t)
+	var nats2 string
+	if strings.Contains(t.Name(), "Federation") {
+		nats2 = startLocalNatsServer(t)
+	} else {
+		nats2 = nats1
+	}
 	grpcServer1, addr1 := NewGrpcServerForTest(t)
 	grpcServer2, addr2 := NewGrpcServerForTest(t)
 
-	events1, err := NewAsyncEvents(nats)
+	events1, err := NewAsyncEvents(nats1)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -220,7 +226,7 @@ func CreateClusteredHubsForTestWithConfig(t *testing.T, getConfigFunc func(*http
 	if err != nil {
 		t.Fatal(err)
 	}
-	events2, err := NewAsyncEvents(nats)
+	events2, err := NewAsyncEvents(nats2)
 	if err != nil {
 		t.Fatal(err)
 	}