(#20281) overwrite existing puppet.conf settings

Whenever you add a value or pass a value to the installer and the puppet.conf
already exists from a pre-existing or prior installation, the new values are
not written to the file. This changes that so that what you pass always
overrides whatever is already there.
Merge pull request #58 from ferventcoder/ticket/master/20281-commandline_override

(#20281) Overwrite Existing puppet.conf Settings