firmware: prepare for our new "-devel" plugin suffix

(cherry picked from commit 27f3a1be)
(cherry picked from commit 2c17a0f7)
(cherry picked from commit 6e5dfc36)

src/opnsense/mvc/app/controllers/OPNsense/Core/Api/FirmwareController.php

 <?php
 
 /**
- *    Copyright (c) 2015-2016 Franco Fichtner <franco@opnsense.org>
+ *    Copyright (c) 2015-2017 Franco Fichtner <franco@opnsense.org>
  *    Copyright (c) 2015-2016 Deciso B.V.
  *    All rights reserved.
  *
@@ -521,11 +521,13 @@ class FirmwareController extends ApiControllerBase
                 if (count($plugin)) {
                     if ($plugin[0] == 'os' || ($type == 'local' && $plugin[0] == 'ospriv') ||
                         ($devel && $type == 'remote' && $plugin[0] == 'ospriv')) {
+                        if ($devel || (count($plugin) < 3 || end($plugin) != 'devel')) {
                             $plugins[$translated['name']] = $translated;
                         }
                     }
                 }
             }
+        }
 
         uksort($packages, function ($a, $b) {
             return strnatcasecmp($a, $b);