* fix(modules/xbps): do not upgrade in check mode
Ensure that while in check mode, this module does not upgrade all
packages on the system.
* chore(modules/xbps): refactor update_cache
Pull out the update_cache logic from the main function.
* feat(modules/xbps): upgrade xbps package itself
Perform an upgrade of the xbps package itself, when necessary.
Otherwise, users' playbooks will fail to install or upgrade packages
when the xbps version is out of date.
See https://github.com/void-linux/xbps/issues/229 for more information.
