A synchronous connect() failure in ipc_connecter can result in Assertion
failed: s == retired_fd (ipc_connecter.cpp:174), as reported in LIBZMQ-294.

This patch fixes the bug, and also an identical problem in tcp_connecter
which has not hit people since TCP connect() usually completes via the
asynchronous code path (poll, out_event).
Signed-off-by: Martin Lucina <martin@lucina.net>