remove apt-get cmds from install_modules.sh

Updates install_modules so that we no longer try to install
puppet via apt-get here. This seems reasonable since we already
installed puppet 2.7 (which has 'module' support) in the
install_jenkins_slave.sh script.

The motivation for this change is to support multiple linux
distributions within openstack-infra and be able to run this
script on Red Hat linux distributions as well.

Change-Id: I1907624d1f934b832216261edf0acd87bfcc4bd2
Reviewed-on: https://review.openstack.org/18903
Reviewed-by: James E. Blair <corvus@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Paul Belanger <paul.belanger@polybeacon.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins