Fix "mf_process_maxfwd_header" retcode in case of parsing errors

(cherry picked from commit 707982e)

modules/maxfwd/maxfwd.c

@@ -152,7 +152,7 @@ static int w_process_maxfwd_header(struct sip_msg* msg, char* str1,char* str2)
 			return 2;
 		/* error */
 		case -2:
-			break;
+			goto error;
 		/* found */
 		case 0:
 			return -1;