fsnotify: reset used_inode and used_vfsmount on each pass

The fsnotify main loop has 2 booleans which tell if a particular mark was
sent to the listeners or if it should be processed in the next pass.  The
problem is that the booleans were not reset on each traversal of the loop.
So marks could get skipped even when they were not sent to the notifiers.

Reported-by: Tvrtko Ursulin <tvrtko.ursulin@sophos.com>
Signed-off-by: Eric Paris <eparis@redhat.com>