[MINOR] cfgparse: fix off-by 2 in error message size

was just looking through the source, and noticed this... :)
(cherry picked from commit 63b76be713784f487e8d0c859a85513642fe7bdc)
(cherry picked from commit a801db6c5ea750f93a3795dbb2e70c03e05bbef4)
diff --git a/src/cfgparse.c b/src/cfgparse.c
index a5f49ac..5394b6b 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1622,7 +1622,7 @@
 		if (warnifnotcap(curproxy, PR_CAP_BE, file, linenum, args[0], NULL))
 			return 0;
 
-		memcpy(trash, "error near 'balance'", 19);
+		memcpy(trash, "error near 'balance'", 21);
 		if (backend_parse_balance((const char **)args + 1, trash, sizeof(trash), curproxy) < 0) {
 			Alert("parsing [%s:%d] : %s\n", file, linenum, trash);
 			return -1;