Incomplete Dispose of WatsonTCPServer

[sancheolz]

This test fails starting from 6.0 version of WatsonTCP:

var server = new WatsonTcpServer("127.0.0.1", 9000);
server.Events.MessageReceived += (_, _) => { Console.WriteLine("srecv"); };
server.Start();
var client = new WatsonTcpClient("127.0.0.1", 9000);
client.Events.MessageReceived += (_, _) => { Console.WriteLine("crecv"); };
client.Connect();
Task.Run(() => { client.SendAsync("aaa"); });
server.Dispose();

It throws

System.AggregateException : One or more errors occurred. (A task was canceled.)
  ----> System.Threading.Tasks.TaskCanceledException : A task was canceled.
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at System.Threading.Tasks.Task.Wait()
   at WatsonTcp.WatsonTcpServer.Dispose(Boolean disposing) in WatsonTcpServer.cs:line 621