fsnotify: Remove special handling of mark destruction on group shutdown

fsnotify: Remove special handling of mark destruction on group shutdown

Currently we queue all marks for destruction on group shutdown and then
destroy them from fsnotify_destroy_group() instead from a worker thread
which is the usual path. However worker can already be processing some
list of marks to destroy so this does not make 100% all marks are really
destroyed by the time group is shut down. This isn't a big problem as
each mark holds group reference and thus group stays partially alive
until all marks are really freed but there's no point in complicating
our lives - just wait for the delayed work to be finished instead.

Reviewed-by: Miklos Szeredi <[email protected]>
Reviewed-by: Amir Goldstein <[email protected]>
Signed-off-by: Jan Kara <[email protected]>