Make use of ping (actually, fping) optional in gluster::simple.

This is useful for environments that don't include fping.
Usage of fping (or similar) is still recommended to make you less likely
to get an error on volume creation if one host isn't up.
Use up-to-date version of the puppet-puppet module.

This incorporates a small fix to avoid installing puppet repositories if
they are already included by the provisioning system.