Make udisks less verbose about "errors" to determine whether unused loop devices are encrypted
This reverts commit 0c048250, which was about an experiment that is not running anymore, and that's moot anyway: with #15281 (closed), we won't need more than 2 loop devices to mount SquashFS'es.
This way, we'll get 4 times less udisks "errors" in the logs, when it fails to determine whether unused loop devices seem to be encrypted or not.
This will mitigate #17351, but it won't fully solve the problem.