policy.json allow all users to do stacks:lookup
policy.json allow all users to do stacks:lookup

We should allow all users, including stack users to do a stacks:lookup
otherwise they need to know both the stack name and ID to make a
request.  This allows us to ensure that any authenticated user can
make a request e.g via heatclient, if they can provide a valid name
or stack ID which they have access to.

Change-Id: Iff992dc5026f436eb22f437ea39b9511ed7fe25d
Partial-Bug: #1291097

redhat-openstack/heat,pratikmallya/heat,jasondunsmore/heat,maestro-hybrid-cloud/heat,noironetworks/heat,rh-s/heat,dims/heat,gonzolino/heat,dragorosson/heat,cryptickp/heat,miguelgrinberg/heat,dragorosson/heat,NeCTAR-RC/heat,openstack/heat,srznew/heat,gonzolino/heat,rh-s/heat,takeshineshiro/heat,maestro-hybrid-cloud/heat,steveb/heat,pshchelo/heat,redhat-openstack/heat,dims/heat,NeCTAR-RC/heat,openstack/heat,noironetworks/heat,srznew/heat,rdo-management/heat,rdo-management/heat,miguelgrinberg/heat,cryptickp/heat,cwolferh/heat-scratch,jasondunsmore/heat,pshchelo/heat,steveb/heat,pratikmallya/heat,cwolferh/heat-scratch,takeshineshiro/heat