Use recursive name lookup for PluginConfig

PluginConfig is based on Gerrit's Config and delegates its
variable resolution to its base config object.
When resolving the configuration names, we do need to perform
a recursive resolution otherwise we would always get an
empty names list.

Change-Id: Iff7a0de4530597fbe45c7aef753363ab6132ecfa

gerrit-server/src/main/java/com/google/gerrit/server/config/PluginConfig.java

@@ -151,6 +151,6 @@ public class PluginConfig {
   }
 
   public Set<String> getNames() {
-    return cfg.getNames(PLUGIN, pluginName);
+    return cfg.getNames(PLUGIN, pluginName, true);
   }
 }