inotify: tail drop inotify q_overflow events

In f44aebcc

 the tail drop logic of events with no file backing
(q_overflow and in_ignored) was reversed so IN_IGNORED events would
never be tail dropped.  This now means that Q_OVERFLOW events are NOT
tail dropped.  The fix is to not tail drop IN_IGNORED, but to tail drop
Q_OVERFLOW.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>