BUG/MINOR: checks: stop polling for write when we have nothing left to send

Since the change of I/O direction, we perform the connect() call and
the send() call together from the top. But the send call must at least
disable polling for writes once it does not have anything left to send.

This bug is partially responsible for the waste of resources described
in issue #253.

This must be backported to 2.0.
1 file changed