qemuxml2(xml|argv)test: Test real state of things with 'x86-kvm-32-on-64'

qemuxml2(xml|argv)test: Test real state of things with 'x86-kvm-32-on-64'

As demonstrated by the qemuxml2xmltest DO_TEST_CAPS_LATEST data based on
the 'x86-kvm-32-on-64' test case the post parse CPU selection code which
fills in the CPU into the definition does not have exactly the same
logic as we used to have when the cpu model was picked when formatting
the commandline.

Change the qemuxml2argv test to use DO_TEST_CAPS_LATEST too as it
doesn't really make sense to test this on fake data.

In addition to 'latest' versions, this also adds second invocation
locked to qemu-4.1.0 which demonstrates the old behaviour.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>