migration: static variables will not be reset at second migration

The static variables in migration_bitmap_sync will not be reset in
the case of a second attempted migration.

Signed-off-by: ChenLiang <chenliang88@huawei.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Merge remote-tracking branch 'remotes/amit-migration/tags/for-2.2-2' into staging

Fix from a while back that unfortunately got ignored.  Dave Gilbert says
it may actually fix a case where autoconverge would break on a repeat
migration (and not just fix stats).

# gpg: Signature made Thu 20 Nov 2014 12:52:41 GMT using RSA key ID 854083B6
# gpg: Good signature from "Amit Shah <amit@amitshah.net>"
# gpg:                 aka "Amit Shah <amit@kernel.org>"
# gpg:                 aka "Amit Shah <amitshah@gmx.net>"

* remotes/amit-migration/tags/for-2.2-2:
  migration: static variables will not be reset at second migration

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>