Use passed priority if set instead of default

Author: iwiznia

src/Client.php

@@ -336,7 +336,7 @@ public function call($method, $headers = [], $body = '')
             $headers['mockRequest'] = true;
         }
 
-        if ($this->commandPriority) {
+        if ($this->commandPriority && !isset($headers['priority'])) {
             $headers['priority'] = $this->commandPriority;
         }