Remove some duplicated code
Save and restore network config on (un)install
Install clean-deploy.sh to a tools/ dir
drop maasdb after purging maas

This way we don't have to figure out how to preseed dbconfig-common to drop the
maasdb, and sometimes it doesn't work, so we'd need to drop it manually
anyways.
Add a run target for running the installer
s/clean-deploy.sh/cloud-uninstall