md: assorted md and raid1 one-liners

md: assorted md and raid1 one-liners

Fix few bugs that meant that:
  - superblocks weren't alway written at exactly the right time (this
    could show up if the array was not written to - writting to the array
    causes lots of superblock updates and so hides these errors).

  - restarting device recovery after a clean shutdown (version-1 metadata
    only) didn't work as intended (or at all).

1/ Ensure superblock is updated when a new device is added.
2/ Remove an inappropriate test on MD_RECOVERY_SYNC in md_do_sync.
   The body of this if takes one of two branches depending on whether
   MD_RECOVERY_SYNC is set, so testing it in the clause of the if
   is wrong.
3/ Flag superblock for updating after a resync/recovery finishes.
4/ If we find the neeed to restart a recovery in the middle (version-1
   metadata only) make sure a full recovery (not just as guided by
   bitmaps) does get done.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>