tm: initiate cancel_bm in t_inject_branch

Make sure we're not canceling unwanted branches if there is some garbage
in the cancel_bm mask

Thanks go to Bogdan Iancu for debugging and fixing

(cherry picked from commit b8dee70)

modules/tm/t_fwd.c

@@ -1014,7 +1014,7 @@ static int dst_to_msg(struct sip_msg *s_msg, struct sip_msg *d_msg)
 int t_inject_branch( struct cell *t, struct sip_msg *msg, int flags)
 {
 	static struct sip_msg faked_req;
-	branch_bm_t cancel_bm;
+	branch_bm_t cancel_bm = 0;
 	str reason = str_init(CANCEL_REASON_200);
 	int rc;