Convert TSIG key names to lowercase.

- See RFC 2845, section 3.4.2

Change-Id: Ie8b5bd3fe449357ddd8f56dcd8992becb1f8b2cf

src/knot/conf/cf-parse.y

@@ -592,6 +592,7 @@ keys:
 		      fqdn);
 	     free($4.t);
 	 } else {
+             knot_dname_to_lower(dname);
              conf_key_t *k = malloc(sizeof(conf_key_t));
              memset(k, 0, sizeof(conf_key_t));