Add a more generic package install mechansim
This splits code in apt_update_upgrade into 'apt-update-upgrade' and
'apt-configure' and 'package-update-upgrade-install'.
The 'package-update-upgrade-install' then uses the generic distro
package mechanisms for acheiving the same goal.
Also, adjusts some of the reboot backoffs and log flushing/sleeping that was
happening there.