We have tests for simple guests with graphics for basically
all other architectures, so it makes sense to include s390x
too.

The input file was generated by running

  $ virt-install \
    --name guest --os-variant fedora29 \
    --vcpus 4 --memory 4096 --disk size=5 \
    --graphics vnc \
    --print-xml

followed by minor tweaks, using a version of virt-manager
that includes commit 7b9de27a990f.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Acked-by: NMichal Privoznik <mprivozn@redhat.com>