Reopening an image should be consistent with opening it, so we should
set BDRV_O_ALLOW_RDWR for any image that is reopened read-write like in
bdrv_open_inherit().
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>