Support for virtio disks was added in commit id 'fceeeda2', 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.