BUILD: log: unused variable svid

This results from previous fix.
diff --git a/src/log.c b/src/log.c
index b13872f..709a66a 100644
--- a/src/log.c
+++ b/src/log.c
@@ -855,7 +855,6 @@
 	struct proxy *be = s->be;
 	struct http_txn *txn = &s->txn;
 	char *uri;
-	const char *svid;
 	struct tm tm;
 	int t_request;
 	int hdr;