Don't return error if already part of channel being joined (#2814)

Makefile

@@ -143,7 +143,7 @@ check-style:
 test: start-docker
 	@echo Running tests
 
-	$(GO) test $(GOFLAGS) -run=$(TESTS) -test.v -test.timeout=240s ./api || exit 1
+	$(GO) test $(GOFLAGS) -run=$(TESTS) -test.v -test.timeout=340s ./api || exit 1
 	$(GO) test $(GOFLAGS) -run=$(TESTS) -test.v -test.timeout=12s ./model || exit 1
 	$(GO) test $(GOFLAGS) -run=$(TESTS) -test.v -test.timeout=120s ./store || exit 1
 	$(GO) test $(GOFLAGS) -run=$(TESTS) -test.v -test.timeout=120s ./utils || exit 1