The capabilities used in test cases should match those used
during normal operation for the tests to make any sense.
This results in the generated command line for a few test
cases (most notably non-x86 test cases that were wrongly
assuming they could use -no-acpi) changing.
https://bugzilla.redhat.com/show_bug.cgi?id=1286709
Now that we have all the pieces in place, we can add the 'iothread=#' to
the command line for the (two) controllers that support it (virtio-scsi-pci
and virtio-scsi-ccw). Add the tests as well...