Followup from D11358#106424 and make policy.locked fully work

Summary: Fast commit. Also forgot to make the config override the existing policy. I *think* this is the right spot and we're good? Ref T6947.

Test Plan: viewed the application settings page for people application and saw the correct overrode setting.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6947

Differential Revision: https://secure.phabricator.com/D11373

src/applications/base/PhabricatorApplication.php

@@ -454,6 +454,11 @@ abstract class PhabricatorApplication implements PhabricatorPolicyInterface {
       return null;
     }
 
+    $policy_locked = PhabricatorEnv::getEnvConfig('policy.locked');
+    if (isset($policy_locked[$capability])) {
+      return $policy_locked[$capability];
+    }
+
     return idx($policy, $capability);
   }