c29152c691
By passing in the format, qemu-img will also check that the file is a
valid instance of the expected format instead of auto-detecting. The
size will also be correct when there previously was a wrong
auto-detection, but it is already only used for checking that the call
was successful.
It looks like this could also avoid wrongly failing checks with the
parent information, but a raw image cannot have a base volume and raw
images are those where the auto-detection might lead to a different
format.
Remove the unused variable $used while at it.
The check for $format in the result became obsolete with 35533c6 ("add
subvol support for directory storage").
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>