sim-auth: Remove watch if open_channel fails

Otherwise open_channel won't be called again after a failure.
diff --git a/src/sim-auth.c b/src/sim-auth.c
index 0e13b53..3c3f35e 100644
--- a/src/sim-auth.c
+++ b/src/sim-auth.c
@@ -367,6 +367,8 @@
 error:
 	__ofono_dbus_pending_reply(&sa->pending->msg,
 			__ofono_error_failed(sa->pending->msg));
+	__ofono_sim_remove_session_watch(sa->pending->session,
+			sa->pending->watch_id);
 	g_free(sa->pending);
 	sa->pending = NULL;
 }