QA: remove the --default-hypervisor option

This option is gone since 1ac0f5e6d2f06a5bf12815e1b92d1338af32833c,
fixing the QA suite to deal with this.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

qa/qa-sample.json

 {
   "name": "xen-test",
   "rename": "xen-test-rename",
-  "default-hypervisor": "xen-pvm",
+  "enabled-hypervisors": "xen-pvm",
 
   "os": "debian-etch",
   "mem": "512M",

qa/qa_cluster.py

@@ -68,9 +68,9 @@ def TestClusterInit():
     cmd.append('--bridge=%s' % bridge)
     cmd.append('--master-netdev=%s' % bridge)
 
-  htype = qa_config.get('default-hypervisor', None)
+  htype = qa_config.get('enabled-hypervisors', None)
   if htype:
-    cmd.append('--default-hypervisor=%s' % htype)
+    cmd.append('--enabled-hypervisors=%s' % htype)
 
   cmd.append(qa_config.get('name'))