minor cleanup in websocket code

[briot]

While reviewing code for PR 209, I noticed the following function aws-net-websocket-registry.adb:

      procedure Watch (WebSocket : Object_Class) is
      begin
         if Is_Registered (WebSocket.Id)
           and then not Watched.Contains (WebSocket.Id)
         then
            Watched.Insert (WebSocket.Id);
            Count := Count + 1;
            Signal_Socket;
         end if;

      exception
         when others =>
            Unregister (WebSocket);
            raise;
      end Watch;

It is slightly un-optimal since it needs to do two lookups when the socket is not watched yet. Perhaps something like the following would be more efficient:

      procedure Watch (WebSocket : Object_Class) is
          Inserted : Boolean;
          Pos : WebSocket_Set.Cursor;
      begin
         if Is_Registered (WebSocket.Id) then
            Watched.Insert (WebSocket.Id, Pos, Inserted);
            if Inserted then
               Count := Count + 1;
               Signal_Socket;
            end if;
        end if;

      exception
         when others =>
            --  ??? Not clear why we would unregister the socket here ? 
            --  also, it is possible that it is still in Watched at this point, and given the first test in this procedure this
            --  might be unexpected behavior.
            Unregister (WebSocket);
            raise;
      end Watch;