New image build infrastructure enabled

[Colin Watson]

A bit later than planned, the new image build infrastructure I described
in https://lists.ubuntu.com/archives/ubuntu-devel/2014-May/038267.html
is now in production and being used for all new live filesystem builds.
Hopefully the main immediate practical effect of this will be that
respin cycles for the milestone release this week will be much faster as
we'll be able to distribute them out to more builders.

There are a couple of features still awaiting deployment, namely builds
from -proposed (needed for stable releases) and builds with extra PPAs
(needed for the new CI engine).  IS has a ticket for this and it should
get done this week.

This will have the effect of slightly increasing the load on our
devirtualised build farm for the time being, because it will be assuming
the additional load previously taken by the livefs builders.  Fear not:
we will shortly be turning the livefs builders into additional Launchpad
builders.  This will give us a net increase in capacity (especially
noticeable on powerpc, I expect), since the livefs builders were not
running builds non-stop beforehand.

Cheers,

-- 
Colin Watson                                       [cjwatson at ubuntu.com]