No longer need to use accelerated ansible version.

The base requirements now use an updated verison of ansible (1.9), so we
do not need to have this install step.

util/packer/jenkins_worker.json

@@ -61,7 +61,6 @@
     "type": "shell",
     "inline": ["cd {{user `playbook_remote_dir`}}",
       ". packer-venv/bin/activate",
-      "pip install -q -U ansible==1.7.1",
       "ansible-playbook run_role.yml -i inventory.ini -c local -e role=test_build_server -vvvv"]
   }]
 }