Fix retrieval of shared firewall_policies

Incorrect rule in the policy.json prevents the visibility
of shared firewall_policies.

Change-Id: I6541d363f1ca4ae89b9dddab41a8f20522e50df8
Closes-bug: 1426586

etc/policy.json

@@ -7,6 +7,7 @@
     "regular_user": "",
     "shared": "field:networks:shared=True",
     "shared_firewalls": "field:firewalls:shared=True",
+    "shared_firewall_policies": "field:firewall_policies:shared=True",
     "external": "field:networks:router:external=True",
     "default": "rule:admin_or_owner",
 
@@ -87,7 +88,7 @@
     "delete_firewall": "rule:admin_or_owner",
 
     "create_firewall_policy": "",
-    "get_firewall_policy": "rule:admin_or_owner or rule:shared_firewalls",
+    "get_firewall_policy": "rule:admin_or_owner or rule:shared_firewall_policies",
     "create_firewall_policy:shared": "rule:admin_or_owner",
     "update_firewall_policy": "rule:admin_or_owner",
     "delete_firewall_policy": "rule:admin_or_owner",