[5.5] Standardize getQueue() (#18501)

* Update DatabaseQueue.php

* Update RedisQueue.php

Author: laurencei

src/Illuminate/Queue/DatabaseQueue.php

@@ -306,7 +306,7 @@ public function deleteReserved($queue, $id)
      * @param  string|null  $queue
      * @return string
      */
-    protected function getQueue($queue)
+    public function getQueue($queue)
     {
         return $queue ?: $this->default;
     }

src/Illuminate/Queue/RedisQueue.php

@@ -253,7 +253,7 @@ protected function getRandomId()
      * @param  string|null  $queue
      * @return string
      */
-    protected function getQueue($queue)
+    public function getQueue($queue)
     {
         return 'queues:'.($queue ?: $this->default);
     }