S390: Adding testcases for s390

Add minimal s390-virtio domain testcase and testcases for virtio serial,
net, disk for the virtio-s390 bus.

Signed-off-by: Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>

tests/qemuxml2argvdata/qemuxml2argv-net-virtio-s390.xml

@@ -0,0 +1,22 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory>219136</memory>
+  <currentMemory>219136</currentMemory>
+  <vcpu>1</vcpu>
+  <os>
+    <type arch='s390x' machine='s390-virtio'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <interface type='user'>
+      <mac address='00:11:22:33:44:55'/>
+      <model type='virtio'/>
+    </interface>
+  </devices>
+</domain>