monitor: convert do_closefd() to QError

Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

monitor.c

@@ -2121,8 +2121,7 @@ static void do_closefd(Monitor *mon, const QDict *qdict, QObject **ret_data)
         return;
     }
 
-    monitor_printf(mon, "Failed to find file descriptor named %s\n",
-                   fdname);
+    qemu_error_new(QERR_FD_NOT_FOUND, fdname);
 }
 
 static void do_loadvm(Monitor *mon, const QDict *qdict)