various fixes (#1267)

* logger: remove Panic log level

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server/grpc: add missing Unlock in Subscribe error

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server: minor code change

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server/grpc: extend test suite with pub/sub testing

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server/grpc: fix invalid check and allow subscriber error to be returned

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* server/grpc: add pubsub tests

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* client/grpc: check for nil req/rsp

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

server/rpc_router.go

@@ -505,7 +505,6 @@ func (router *router) Subscribe(s Subscriber) error {
 }
 
 func (router *router) ProcessMessage(ctx context.Context, msg Message) (err error) {
-
 	defer func() {
 		// recover any panics
 		if r := recover(); r != nil {
@@ -516,16 +515,13 @@ func (router *router) ProcessMessage(ctx context.Context, msg Message) (err erro
 	}()
 
 	router.su.RLock()
-
 	// get the subscribers by topic
 	subs, ok := router.subscribers[msg.Topic()]
-	if !ok {
-		router.su.RUnlock()
-		return nil
-	}
-
 	// unlock since we only need to get the subs
 	router.su.RUnlock()
+	if !ok {
+		return nil
+	}
 
 	var errResults []string