Revert "Stop managing puppet apt pins"

This reverts commit 5be2e2f18ac1f4489be760717519252ba20d4fba.

Yay!  We've sucessfully upgraded to puppet3 and the sun is shining!
Start managing apt pins for puppet again, and also, set the default
to be 3.x everywhere.

Change-Id: I80db5b5e154a3849914aa348e1eabadd0a2ad936
Merge "Revert "Stop managing puppet apt pins""