Bump default cirros version to 0.6.2

Cirros has made a new release, including a newer kernel that should fix
some issues when using nested virtualization.

Related-Bug: 2023559
Change-Id: I63469371b13801094a3ee1baae6e343999fbefa5
diff --git a/doc/source/guides/nova.rst b/doc/source/guides/nova.rst
index d0fb274..705d427 100644
--- a/doc/source/guides/nova.rst
+++ b/doc/source/guides/nova.rst
@@ -122,7 +122,7 @@
 .. code-block:: shell
 
   $ openstack --os-compute-api-version 2.37 server create --flavor cirros256 \
-      --image cirros-0.6.1-x86_64-disk --nic none --wait test-server
+      --image cirros-0.6.2-x86_64-disk --nic none --wait test-server
 
 .. note:: ``--os-compute-api-version`` greater than or equal to 2.37 is
           required to use ``--nic=none``.