(packaging) Add Trusty cow to stable branch

This will let us build packages for trusty in the next hiera release off
the stable branch. This change is already in the master branch

Author: melissa

ext/build_defaults.yaml

@@ -2,7 +2,7 @@
 packaging_url: 'git://github.com/puppetlabs/packaging.git --branch=master'
 packaging_repo: 'packaging'
 default_cow: 'base-squeeze-i386.cow'
-cows: 'base-lucid-i386.cow base-precise-i386.cow base-quantal-i386.cow base-sid-i386.cow base-squeeze-i386.cow base-stable-i386.cow base-testing-i386.cow base-unstable-i386.cow base-wheezy-i386.cow base-saucy-i386.cow'
+cows: 'base-lucid-i386.cow base-precise-i386.cow base-quantal-i386.cow base-sid-i386.cow base-squeeze-i386.cow base-stable-i386.cow base-testing-i386.cow base-trusty-i386.cow base-unstable-i386.cow base-wheezy-i386.cow base-saucy-i386.cow'
 pbuild_conf: '/etc/pbuilderrc'
 packager: 'puppetlabs'
 gpg_name: 'info@puppetlabs.com'