Add a basic sanity reboot test collecting AVCs
    
    From time to time there's systemd update with new features which could break an
    SELinux enabled system. In order to minimize possible damage on composes we need
    to be sure that a system can boot with new systemd and it doesn't generate any
    AVC denial.
    
    This test reboots a machine and collects AVC, USER_AVC and SELINUX_ERR audit
    messages into avc.log file which is propagated as test artifact.