Review docker storage disk code

[hassenius]

The code dealing with storage for docker might need an overhaul.
Seems somewhat inconsistent, as looks like some code is formatting the disk as ext4 and other code refers to devicemapper with lvm.

In light of Overlay2 having been the default docker storage driver for Ubuntu for a long time, and being the default driver for RHEL since 7.5, we might reconsider