Add puppetmaster-passenger to list of 2.7.x pins

In order to install the puppetmaster, puppetmaster-passenger also needed to be
added to the packages pinned to the 2.7.x series in the puppetlabs repo

Change-Id: Ia1bfa0471eb35bb76056431ff0c3211ff7599c0f
Reviewed-on: https://review.openstack.org/20049
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins