qemu-iotests/199: check persistent bitmaps

Check that persistent bitmaps are not stored on source and that bitmaps
are persistent on destination.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Message-Id: <20200727194236.19551-20-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>