Remove descriptor from NewDescriptors when it is detached to fix this issue.
Fix crash on attach/detach in the same tick
Please hold off on merging this; it seems to introduce a failure in tests/test_idle_connection.rb.
It only fails when EM.epoll is set, regardless of this patch being applied or not.
It seems that this patch makes the test_idle_time(TestIdleConnection) to fail:
<0> expected but was
fix idle test with epoll (cc #427)
Fix crash on attach/detach in the same tick (eventmachine#427).