(MODULES-3037) Reset config/checking values helpers
(MODULES-3037) Reset config/checking values helpers

- Added `get_xml_value` to take config file output and verify configuration
  values from it.
- Added `backup_config`/`reset_config` to copy a backup of the config file
  and reset it when a test is complete.

ThoughtCrhyme/puppetlabs-chocolatey,ThoughtCrhyme/puppetlabs-chocolatey