Log early boot of Ironic VMs to serial with sgabios

This adds sgabios to the list of packages for Ironic and configures
the libvirt domain to redirect BIOS messages to serial via sgabios,
when console logging is enabled.  The sgabios package in Ubuntu
currently has an apparmor bug, so that is worked around here.

This allows visibility into early boot of Ironic nodes and should
help get to the bottom of a frequent failure we're seeing in the gate.

Change-Id: Ifd18851e2d23d198d36e67883a81afc6a92d2a58
Related-Bug: #1393099
Merge "Log early boot of Ironic VMs to serial with sgabios"