contint: get rid of misc::pbuilder on slaves

Our class misc::pbuilder creates a bunch of pbuilder/cowbuilder images
on the disk.  To build Debian packages we are using
jenkins-job-debian-glue which installs package dependencies and take
care of creating cowbuilder images.

We just have to make sure the images are going to be build under
/mnt/pbuilder to have enough disk space.

Change-Id: I45317e87ad2f1a8c0cf699b1fac0a7d3135151b7
contint: directory to hold debian-glue packages

Creates /data/project/debianrepo to have debian-glue generated packages
hosted on a shared space.

Needs to update the Jenkins debian-glue jobs to point to it.

Change-Id: If356c8156ed18ff26b8d81ff240e9fd9523bc28a
Merge changes If356c815,I45317e87 into production

* changes:
  contint: directory to hold debian-glue packages
  contint: get rid of misc::pbuilder on slaves