With the code as it is, it is possible for oustanding clear region requests
never to get flushed when a mirror is deactivated or suspended.  This means
there will always be some resync work required when a mirror is activated,
even though it may very well be in-sync.

Always requesting the flush doesn't hurt us.  This is because the log tracks
whether any changes occurred and, if not, no flush is performed.
Signed-off-by: NJonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>