Issue 50122 - Selinux test for presence
    
    Description:  Selinux is not present on all systems. Trying to
    import python-selinux when it's not available fails, but we
    can not guarantee that the with_selinux flag to defaults is
    correct because some systems build with selinux but may not
    have it enabled. We should check if we can access the tools
    instead, and skip them (with warnings) if we can't make changes
    
    https://pagure.io/389-ds-base/issue/50122
    
    Reviewed by: mreynolds