Refactor osdetect for rhel family OSes

[fabi200123]

This PR refactors the osdetect for the OSes that are RHEL related. It adds a common.py where the detect_os_from_os_release is defined to return the proper info from /etc/os-release:

    return {
        "os_type": constants.OS_TYPE_LINUX,
        "distribution_name": distribution_name,
        "release_version": version,
        "friendly_release_name": "%s Version %s" % (
            distribution_name, version)}

It keeps the previous format for distribution_name based on DISTRO_IDENTIFIER.