(SERVER-256) Fix failing FOSS upgrade smoke test.

* This adds a method, package_upgrade, which always upgrades the given package
  regardless of whether there are changes both to the new version of the config
  file and to the previously-installed version.
* Also removes the puppet_server_name parameter on install_puppet_server which
  is unnecessary since as it turns out there is only actually one package name
  for puppet_server.
* Also removes some completely dead code which attemptes to modify
  SERVICE_NUM_RETRIES in puppetserver's defaults file. This variable is no
  longer used.
If you go the "yum reinstall" route, I think you'd be able to avoid having to detect the currently installed version which needs to be reinstalled.  I think you'd have to purge the configuration files that may have changed with this approach, though, or the reinstall won't reset the changed files back to their defaults.  So maybe that would make the remove, install, install approach easier so long as you detect the right version to install at each step?