Test tweaks.
Lose the ->flush; leftovers from some groping about.

	modified:   lib/POEx/ZMQ3/Role/Sockets.pm
return from read/write if zsock is marked as closing.

	modified:   lib/POEx/ZMQ3/Role/Sockets.pm
... don't need that ->close, either

	modified:   lib/POEx/ZMQ3/Role/Sockets.pm
Only yield zsock_cleanup after deselecting

	modified:   lib/POEx/ZMQ3/Role/Sockets.pm