Improve testing of an explicitly requested USB controller without a
model being provided.
For this purpose the 'usb-controller' case is renamed to
'usb-controller-default-i440fx'; 'usb-controller-default-q35' is moved
up to form a group. In both cases tests are covnerted to use
DO_TEST_CAPS_LATEST.
A new 'usb-controller-default-isapc' negative test case is added for
symmetry.
The negative test case 'usb-controller-default-unavailable-q35' is
converted to use latest caps, but stripping the default controller
instead of using fake caps. Additionally for symmetry
'usb-controller-default-unavailable-i440fx' is added although that
doesn't cause failure, but rather a graceful downgrade to use '-usb'.
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
