Improve xio_ev_loop_stop() commit so it will not re-arm (epoll(ADD)) multiple times from self thread

Signed-off-by: Alex Rosenbaum <Alexr@mellanox.com>
Merge pull request #4 from rosenbaumalex/master

Improve xio_ev_loop_stop() commit so it will not re-arm (epoll(ADD)) multiple times from self thread