tests: Fix some usb-controller-*-unavailable cases

tests: Fix some usb-controller-*-unavailable cases

These tests are intended to show what happens when the device
that libvirt would use by default is not available in QEMU by
dropping the corresponding capabilities, but we're not doing
that correctly at the moment and so we still get the default
USB controller instead of a failure.

Specifically, we should be dropping all capabilities related
to devices that might be used as default or automatic USB
controllers for the machine type so that libvirt will report
an error, but for these few tests we are currently only
listing a subset of the capabilities that we should be
dropping.

Note that the usb-controller-automatic-unavailable tests are
still behaving the same despite dropping all the expected
capabilities: the reason is that, for that scenario, we're
not currently checking whether the device is available before
using it. That's a separate issue that will be addressed in an
upcoming commit.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>