qemuxml2argvtest: Switch memory-hotplug-dimm-addr to latest caps

qemuxml2argvtest: Switch memory-hotplug-dimm-addr to latest caps

So far, we are testing memory-hotplug-dimm-addr against a set of
explicitly listed capabilities. While this works, lets switch it
to DO_TEST_CAPS_LATEST() so that the latest capabilities are
used. This in turn means, we have to update the <emulator/>
because the latest capabilities don't contain caps for
qemu-system-i386.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>