child-cfg: Actually force narrowing TS in transport mode only as initiator

Closes strongswan/strongswan#2830

Fixes: ad1ad2159f ("child-cfg: Use traffic selector list")

src/libcharon/config/child_cfg.c

@@ -300,7 +300,7 @@ linked_list_t *child_cfg_select_ts(child_cfg_t *cfg, bool local,
 
 	/* force replacing non-dynamic TS to the IPs in transport mode, but only
 	 * when proposing as initiator */
-	force = supplied && is_transport_mode(this);
+	force = !supplied && is_transport_mode(this);
 
 	result = ts->select(ts, supplied, hosts, force, &narrowed);
 	if (narrowed)