inotify, fanotify: replace fsnotify_put_group() with fsnotify_destroy_group()

Currently in fsnotify_put_group() the ref count of a group is decremented and if
it becomes 0 fsnotify_destroy_group() is called. Since a groups ref count is only
at group creation set to 1 and never increased after that a call to fsnotify_put_group()
always results in a call to fsnotify_destroy_group().
With this patch fsnotify_destroy_group() is called directly.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>