Pin jenkins jobs of groups portal to precise

The groups portal based on Drupal 7.x and as some trusty php
packages is buggy, so we need to do a careful testing before
we can switch from php 5.3 to php 5.5.

Change-Id: I3e42448a8c245a30e8b5b617b345d061afb4e34d
Merge "Pin jenkins jobs of groups portal to precise"