BUG/MAJOR: ssl: fix segfault on connection close using async engines.

BUG/MAJOR: ssl: fix segfault on connection close using async engines.

This patch ensure that the ASYNC fd handlers won't be wake up
too early, disabling the event cache for this fd on connection close
and when a WANT_ASYNC is rised by Openssl.

The calls to SSL_read/SSL_write/SSL_do_handshake before rising a real read
event from the ASYNC fd, generated an EAGAIN followed by a context switch
for some engines, or a blocked read for the others.

On connection close it resulted in a too early call to SSL_free followed
by a segmentation fault.