Relax the condition about a unique uuid for convert, only print a
warning. In case we copy the uuid, it's expected that at the time the
conversion starts the uuid is not unique as it sill exists on the source
filesystem.
In case user sets the uuid manually but it's still the same one as on
the source filesystem we should also allow that, so it warns in this
case as well.
Update the test so it creates a block device where the uuid would be
also cached by blkid and lets the non-unique check succeed.
Issue: #404
Signed-off-by: David Sterba <dsterba@suse.com>
David Sterba