macos: avoid leaking iocount on synthetic fsevents

macos: avoid leaking iocount on synthetic fsevents

in certain cases we could leak an iocount. clean up even if
our event couldn't be run

Reviewed-on: http://gerrit.openafs.org/8777
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit cf150252b688dff0224f32be66d88347d1d94b37)

Change-Id: Id8c94bee3663507d31c0e0dc719693d82f90a151
Reviewed-on: http://gerrit.openafs.org/8791
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Paul Smeddle <paul.smeddle@gmail.com>