Revert "(#17458) Load 'puppet' at the right time"

Commit b5ed15baadffb22b789cebfab7a76e2ab43c7d14 attempted to require
'puppet' at the right time, but failed. The command_line required puppet
before the application was required and its run_mode determined. As a
result, puppet master was using the default :user run_mode, causing
its pidfile to be named 'agent.pid' among other things.

This comit reverts b5ed15ba.