Can gd2 take a directory as requirement (instead of 'add-device') for loopback bricks? #1502

Observed behavior

Device registration often fails in container world. Specifically when I am trying to run in minikube etc.

Expected/desired behavior

Considering we now have 'loopback' brick support, all we need is a directory as an argument. With that, gd2 has no dependency on devices.

Other useful information

This will be really useful for GD2 to succeed on different filesystem and other eco-systems where people doesn't use LVM and XFS.

Also helps us in GCS world.