set-task-priority fix permission error

Fixes: https://pagure.io/koji/issue/2969

cli/koji_cli/commands.py

@@ -6618,6 +6618,10 @@ def handle_set_task_priority(goptions, session, args):
 
     activate_session(session, goptions)
 
+    if not session.hasPerm('admin'):
+        logged_user = session.getLoggedInUser()
+        error("admin permission required (logged in as %s)" % logged_user['name'])
+
     for task_id in tasks:
         try:
             session.setTaskPriority(task_id, options.priority, options.recurse)