Do wait for connection in the server socket.

Do wait for connection in the server socket.

The code returned immediately from wxSocketBase::DoWait() if it wasn't
connected but it only made sense for the client sockets, not server ones which
could be calling this function precisely in order to wait until a connection
is made.

Also added a test for this bug in the sockets/server sample.

Closes #11107.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61726 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775