Update to latest HEAD.
    
    - Actually run the groups update config. when not in objects mode. BZ 1002439.
    - Implement pkg.remote_url for YumLocalPackage. BZ 1016148.
    - UpdateNotice.xml(): sanitize pkg['epoch']. BZ 1020540.
    - yum-cron: support download/install with update_messages==False. BZ 1018068.
    - Fix some bugs in setopt for repo config. entries. BZ 1023595.
    - Add loop limit for depsolving. BZ 1017840.
    - Add yum-makecache systemd service, force network updates on for better UI.