Fix: handle invalid ops pointer in relayd_close()

Fix: handle invalid ops pointer in relayd_close()

Add a lttcomm socket ops pointer check before calling the close
operation of the socket. This can happen if the socket object was
allocated but NOT created.

Furthermore, a fallback is added if no ops pointer is found, the
close(3) system call is used.

This commit also fixes the fact that relayd_close could have been called
on a socket with an invalid operation pointer during the relayd object
creation process in an error path.

Fixes #429

Signed-off-by: David Goulet <dgoulet@efficios.com>