[PATCH] md: make sure recovery happens when add_new_disk is used for hot_add

Currently if add_new_disk is used to hot-add a drive to a degraded array,
recovery doesn't start ...  because we didn't tell it to.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>