fsmonitor: move untracked-cache invalidation into helper functions

fsmonitor: move untracked-cache invalidation into helper functions

Move the call to invalidate the untracked-cache for the FSEvent
pathname into the two helper functions.

In a later commit in this series, we will call these helpers
from other contexts and it safer to include the UC invalidation
in the helpers than to remember to also add it to each helper
call-site.

This has the side-effect of invalidating the UC *before* we
invalidate the ce_flags in the cache-entry.  These activities
are independent and do not affect each other.  Also, by doing
the UC work first, we can avoid worrying about "early returns"
or the need for the usual "goto the end" in each of the
handler functions.

Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>