Fix beaker under centos
Fix beaker under centos

beaker-puppet_install_helper 0.6.0 has made the PUPPET_INSTALL_TYPE now
default to agent which was the previous behavior we had when running
under puppet 4. Since puppet 3 is now officially EOL, this switches the
defaut to assume puppet agent packaging rather than the foss version.

Change-Id: I3243f9d7bdb19840f6462c5b6b237c2314a71fbe

openstack/puppet-openstack-integration,openstack/puppet-openstack-integration,openstack/puppet-openstack-integration