block/qcow2-bitmap: get rid of bdrv_has_changed_persistent_bitmaps

block/qcow2-bitmap: get rid of bdrv_has_changed_persistent_bitmaps

Firstly, no reason to optimize failure path. Then, function name is
ambiguous: it checks for readonly and similar things, but someone may
think that it will ignore normal bitmaps which was just unchanged, and
this is in bad relation with the fact that we should drop IN_USE flag
for unchanged bitmaps in the image.

Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Reviewed-by: John Snow <[email protected]>
Message-id: 20190927122355[email protected]
Signed-off-by: John Snow <[email protected]>