(#8443) Clean up gems install script
(#8443) Clean up gems install script

This change cleans up the gems install script to provide more
information about what is executing on the remote system.  Specifically,
calling out running puppet agent --test and ensuring the output of
puppet agent is also connected back to the cloud back install action to
provide end user feedback when Puppet runs for the first time.

Reviewed-by: Dan Bode

puppetlabs/puppetlabs-cloud_provisioner,16nsk/puppetlabs-cloud_provisioner,puppetlabs/puppetlabs-cloud_provisioner,amos6224/puppetlabs-cloud-provisioner