tests: Create privileged config for QEMU driver

tests: Create privileged config for QEMU driver

Our QEMU test suite effectively covers the qemu:///system
scenario, and we have to partially replace the unprivileged
config with its privileged equivalent after the fact to keep up
the illusion.

Instead of jumping through these extra hoops, we can simply
start with a privileged configuration matching the privileged
driver we're creating for test programs.

This change highlights that we were missing a couple of
overrides, specifically in the tests for passt and dbus. Now
that we're creating a privileged config, this kind of issue
shouldn't be able to slip into the test suite.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>