[BUG] config: fix endless loop when parsing "on-error"

An arg index increment was missing causing the same arg to be parsed
in an endless loop. Proabably a merge conflict that remained undetected.

src/cfgparse.c

@@ -3389,6 +3389,7 @@ int cfg_parse_listen(const char *file, int linenum, char **args, int kwm)
 					err_code |= ERR_ALERT | ERR_FATAL;
 					goto out;
 				}
+				cur_arg += 2;
 			}
 			else if (!defsrv && !strcmp(args[cur_arg], "source")) {  /* address to which we bind when connecting */
 				int port_low, port_high;