qemu_cgroup: Kill qemuSetupHostSCSIDeviceCgroup
    
    There's no need for this function. Currently it is passed as a
    callback to virSCSIDeviceFileIterate(). However, SCSI devices
    have just one file path. Therefore we can mimic approach used in
    qemuDomainGetHostdevPath() to get path and call
    virCgroupAllowDevicePath() directly.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
    Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>