qemu: Add support for using AES secret for SCSI hotplug
    
    Support for virtio disks was added in commit id 'fceeeda', but not for
    SCSI drives. Add the secret for the server when hotplugging a SCSI drive.
    No need to make any adjustments for unplug since that's handled during
    the qemuDomainDetachDiskDevice call to qemuDomainRemoveDiskDevice in
    the qemuDomainDetachDeviceDiskLive switch.
    
    Added a test to/for the command line processing to show the command line
    options when adding a SCSI drive for the guest.