Unexpected closing of eventfd may be very hard to debug as kernel may
reuse just closed fd number. To avoid queuing new element to queue
with closed eventfd let's invalidate fd in nqueue_cleanup().
Change-Id: I3e9328dfd713fc29d2adbed68dd1a1b35770e6a9 Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>