An md array can be stopped leaving all the setting still in place, or it can
torn down and destroyed.  set_capacity and other change notifications only
happen in the latter case, but should happen in both.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>