Review and address deltas between current trunk and Xav's branch

I've identified that we have some deltas between cs:~canonical-bootstack/infra-node-2 (charmhub: canonical-bootstack-infra-node-2) and the CharmHub infra-node charm.

This basically comes out to deltas between the git.launchpad.net/~xavpaice/charm-infra-node repo and the git.launchpad.net/charm-infra-node repo.

The xavpaice branch completely precedes the current charmhub code; its latest commit preceeds the first charmhub commit. However, it appears that some of the bits of that code were dropped in the creation of this new branch. I don't know the reason, but these branches appear to have a significant overlap of code, but yet do not share any commit history; it's like the files were copied from one repo to another without copying the commit history.

This matters because we have some clouds running on the old code, and upgrading to the new code means dropping some of the functionality from the old charm.

Are we sure we don't need the functionality which was dropped? If so, that's fine, but I want to ensure it's a conscious decision rather than an accidental miss.

Here is a summary of the deltas I see betweeen the two git branches (xav's repo on the add_charmcraft branch vs. the new repo on the master branch):

* config.yaml: dropped options for nagios_alert_if_juju_enabled, backup_maas, backup_store_offsite
* src/files/scripts/backup.py: appears used by the maasbackup cron job
* src/templates/cron/maasbackup.j2: template for the maasbackup cron job
* src/templates/sudoers/jujumanage.j2: jujumanage user sudoers template