Don't install Nova policy.json
Don't install Nova policy.json

Nova ships with an empty policy.json file which it does not need.
oslo.policy previously required the empty file to be there but as of
version 1.14.0 it is possible to run with no policy file at all. Since
there are no policies defined in the sample file let's no install it.

Change-Id: I85a251376dfe38caa4b100861bf764014a98bc37
Depends-On: I09fa842ffbe75bed269cef6edc9c82d18bfe9297

dtroyer/devstack,richliu/devstack,openstack-dev/devstack,dtroyer/devstack,group-policy/devstack,bswartz/devstack,group-policy/devstack,openstack-dev/devstack,noironetworks/devstack,richliu/devstack,nawawi/openstack,nawawi/openstack,bswartz/devstack,noironetworks/devstack