tm: fix branches clearing lumps

- fix bug introduced in 610cb93
(cherry picked from commit 6a55e42edd0cf0ac82b2099a74b4896fdc801145)

modules/tm/t_fwd.c

@@ -232,8 +232,6 @@ static int prepare_new_uac( struct cell *t, struct sip_msg *i_req,
 #endif
 	add_rm_backup = i_req->add_rm;
 	body_lumps_backup = i_req->body_lumps;
-	i_req->add_rm=0;
-	i_req->body_lumps=0;
 	if (unlikely(i_req->add_rm)){
 		i_req->add_rm = dup_lump_list(i_req->add_rm);
 		if (unlikely(i_req->add_rm==0)){