Ensure 'agent' subcommand is executed

Ensure 'agent' subcommand is executed when PUPPET_SERVER is set in the puppet environment.
Merge branch 'fix/3.1.x/suse_init' into 3.1.x

* fix/3.1.x/suse_init:
  Ensure 'agent' subcommand is executed
Merge branch '3.1.x'

* 3.1.x:
  Ensure 'agent' subcommand is executed

closes #1520