Add example of specifying mostDisruptiveAllowedAction for instance (G…

…oogleCloudPlatform#609)

Deployment Manager now supports the ability to specify the
mostDisruptiveAllowedAction when updating a Compute instance. The full
set of valid values are detailed in the Compute Engine documentation
for the update API at https://cloud.google.com/compute/docs/reference/rest/v1/instances/update

google/resource-snippets/compute-v1/instance.jinja

@@ -28,3 +28,4 @@ resources:
     labels:
       somelabel: {{ properties["somelabel"] or "macano" }}
       fixedlabel: chanapulana
+    mostDisruptiveAllowedAction: RESTART