MINOR: init: exit() after pre-check upon error

Add a test on the err_code variable so we don't go further if one of the
pre-check callback failed.
diff --git a/src/haproxy.c b/src/haproxy.c
index 02690ed..ec40a64 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2117,6 +2117,11 @@
 	list_for_each_entry(prcf, &pre_check_list, list)
 		err_code |= prcf->fct();
 
+	if (err_code & (ERR_ABORT|ERR_FATAL)) {
+		ha_alert("Fatal errors found in configuration.\n");
+		exit(1);
+	}
+
 	err_code |= check_config_validity();
 	for (px = proxies_list; px; px = px->next) {
 		struct server *srv;