(PCP-428) restart_host_run_puppet.rb transient fails on ubuntu1404
(PCP-428) restart_host_run_puppet.rb transient fails on ubuntu1404

This change tries to make the restart_host test more robust by using two
sleeps.  One to ensure the agent is actually rebooted (see BKR-812) and
one to retry up to 10 times until pxp-agent is back up.

[skip ci]

puppetlabs/pxp-agent,puppetlabs/pxp-agent,puppetlabs/pxp-agent