Provide an 'ensure' option to the puppet_reporter class.

This ensure option can be used to uninstall or install the
agent, its configs, etc. If set to 'absent', it will properly
uninstall the entire agent.
The 'token' is not necessary if we're purging the package.
Bugfix: Pull out uncreated variable.
Merge pull request #3 from Nextdoor/add_ensure_to_puppet_reporter

Add ensure to puppet reporter