Fix unpause server policy to be admin_or_owner

unpause server API policy is default to admin_or_owner[1] but API
is allowed for everyone.

We can see the test trying with other project context can access the API
- https://review.opendev.org/#/c/716161/

This is because API does not pass the server project_id in policy target[2]
and if no target is passed then, policy.py add the default targets which is
nothing but context.project_id (allow for everyone who try to access)[3]

This commit fix this policy by passing the server's project_id in policy
target.

Closes-bug: #1869841
Partial implement blueprint policy-defaults-refresh

[1]
- eb6bd04e4c/nova/policies/pause_server.py (L38)
[2]
- eb6bd04e4c/nova/api/openstack/compute/pause_server.py (L58)
[3]
- c16315165c/nova/policy.py (L191)

Change-Id: Iacfaec63eb380863657b44c7f5ff14f6209e3857

nova/api/openstack/compute/pause_server.py

@@ -55,8 +55,9 @@ class PauseServerController(wsgi.Controller):
     def _unpause(self, req, id, body):
         """Permit Admins to unpause the server."""
         ctxt = req.environ['nova.context']
-        ctxt.can(ps_policies.POLICY_ROOT % 'unpause')
         server = common.get_instance(self.compute_api, ctxt, id)
+        ctxt.can(ps_policies.POLICY_ROOT % 'unpause',
+                 target={'project_id': server.project_id})
         try:
             self.compute_api.unpause(ctxt, server)
         except exception.InstanceIsLocked as e:

nova/tests/unit/api/openstack/compute/test_pause_server.py

@@ -114,7 +114,12 @@ class PauseServerPolicyEnforcementV21(test.NoDBTestCase):
         pause_mock.assert_called_once_with(self.req.environ['nova.context'],
                                           instance)
 
-    def test_unpause_policy_failed(self):
+    @mock.patch('nova.api.openstack.common.get_instance')
+    def test_unpause_policy_failed(self, get_instance_mock):
+        instance = fake_instance.fake_instance_obj(
+            self.req.environ['nova.context'],
+            user_id=self.req.environ['nova.context'].user_id)
+        get_instance_mock.return_value = instance
         rule_name = "os_compute_api:os-pause-server:unpause"
         self.policy.set_rules({rule_name: "project:non_fake"})
         exc = self.assertRaises(