Fix for Configure_server_connection_listen_backlog test

[pepone]

Fix #4099

[pepone]

  IceRpc.Tests test net9.0 succeeded (25.2s)
  IceRpc.Tests test net8.0 failed with 1 error(s) (25.7s)
    C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTransportTests.cs(196): error TESTERROR:
      IceRpc:Tests:Transports:Tcp:TcpTransportTests:Configure_server_connection_listen_backlog (621ms): Error Message:   Assert.That(connections, Has.Count.LessThanOrEqualTo(30))
        Expected: property Count less than or equal to 30
        But was:  31

      Stack Trace:
         at IceRpc.Tests.Transports.Tcp.TcpTransportTests.Configure_server_connection_listen_backlog() in C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTran
      sportTests.cs:line 196
         at IceRpc.Tests.Transports.Tcp.TcpTransportTests.Configure_server_connection_listen_backlog() in C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTran
      sportTests.cs:line 198
         at NUnit.Framework.Internal.TaskAwaitAdapter.GenericAdapter`1.BlockUntilCompleted()
         at NUnit.Framework.Internal.MessagePumpStrategy.NoMessagePumpStrategy.WaitForCompletion(AwaitAdapter awaiter)
         at NUnit.Framework.Internal.AsyncToSyncAdapter.Await[TResult](Func`1 invoke)
         at NUnit.Framework.Internal.AsyncToSyncAdapter.Await(Func`1 invoke)
         at NUnit.Framework.Internal.Commands.TestMethodCommand.RunTestMethod(TestExecutionContext context)
         at NUnit.Framework.Internal.Commands.TestMethodCommand.Execute(TestExecutionContext context)
         at NUnit.Framework.Internal.Execution.SimpleWorkItem.<>c__DisplayClass3_0.<PerformWork>b__0()
         at NUnit.Framework.Internal.ContextUtils.<>c__DisplayClass1_0`1.<DoIsolated>b__0(Object _)

      1)    at IceRpc.Tests.Transports.Tcp.TcpTransportTests.Configure_server_connection_listen_backlog() in C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpT
      ransportTests.cs:line 196

Sill getting an sporadic failure when running in a loop.

[pepone]

Tried with 35, but still got a failure with 47 accepted connections:

    C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTransportTests.cs(196): error TESTERROR:
      IceRpc:Tests:Transports:Tcp:TcpTransportTests:Configure_server_connection_listen_backlog (604ms): Error Message:   Assert.That(connections, Has.Count.LessThanOrEqualTo(35))
        Expected: property Count less than or equal to 35
        But was:  47

      Stack Trace:
         at IceRpc.Tests.Transports.Tcp.TcpTransportTests.Configure_server_connection_listen_backlog() in C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTran
      sportTests.cs:line 196
         at IceRpc.Tests.Transports.Tcp.TcpTransportTests.Configure_server_connection_listen_backlog() in C:\Users\jose\source\repos\icerpc-csharp\tests\IceRpc.Tests\Transports\Tcp\TcpTran
      sportTests.cs:line 198
         at NUnit.Framework.Internal.AsyncToSyncAdapter.Await[TResult](Func`1 invoke)
         at NUnit.Framework.Internal.Commands.TestMethodCommand.RunTestMethod(TestExecutionContext context)
         at NUnit.Framework.Internal.Commands.TestMethodCommand.Execute(TestExecutionContext context)
         at NUnit.Framework.Internal.Execution.SimpleWorkItem.<>c__DisplayClass3_0.<PerformWork>b__0()
         at NUnit.Framework.Internal.ContextUtils.<>c__DisplayClass1_0`1.<DoIsolated>b__0(Object _)

[bernardnormier]

After looking at this test, I understand that when duplexConnection.ConnectAsync() completes successfully in a client, it means:

• the server accepted the connection (via AcceptAsync on the listener), or
• the server didn't accept the connection yet but kept in the its listen backlog, and this listen backlog isn't full yet (with some wiggle room apparently)

It would be nice to explain this in the remarks of the duplex connection APIs.