Add a missing unlock within error handling

(closes issue #13176)
Reported by: pj


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@134005 65c4cc65-6c06-0410-ace0-fbb531ad65f3

funcs/func_config.c

@@ -146,6 +146,7 @@ static int config_function_read(struct ast_channel *chan, const char *cmd, char
 	if (!(val = ast_variable_retrieve(cfg, args.category, args.variable))) {
 		ast_log(LOG_ERROR, "'%s' not found in [%s] of '%s'\n", args.variable, 
 			args.category, args.filename);
+		AST_RWLIST_UNLOCK(&configs);
 		return -1;
 	}