reference leak on error in controlconf.c:control_respond

on inspection this should be fixed.

diff --git a/bin/named/controlconf.c b/bin/named/controlconf.c
index 5d776e638e..706ec0b9ec 100644
--- a/bin/named/controlconf.c
+++ b/bin/named/controlconf.c
@@ -371,8 +371,10 @@ control_respond(isc_nmhandle_t *handle, isc_result_t result, void *arg) {
        }
 
        return;
+
 cleanup:
        conn_cleanup(conn);
+       isc_nmhandle_detach(&conn->cmdhandle);
 }
 
 static void