Create a 20auto-upgrades file to fix unattended upgrades.

14.10 has added a new file to the apt deb called 20auto-upgrades that is
run later than our old periodic config that disabled auto updates. This
patch enables them by overwriting the new file.
Merge branch 'master' of git:infrastructure/dtg-puppet
Fix dac53's public key
Merge branch 'master' of dac53.dtg.cl.cam.ac.uk:/etc/puppet-bare