Don't run dsvm tests on hacking only changes

If the change is only hacking of Nova, don't run the dsvm changes
for avoiding much test operation time.

Change-Id: I01f9caa083dc7d06c850c9f466a6b38fbd42d209

zuul/layout.yaml

@@ -649,6 +649,7 @@ jobs:
           - ^.*\.rst$
           - ^doc/.*$
           - ^nova/tests/.*$
+          - ^nova/hacking/.*$
           - ^tools/.*$
           - ^tox.ini$
       - project: ^openstack/ironic$