myql_common.c:gw_send_change_user_to_backend checks func.write for 0 and 1

mysql_client.c:gw_MySQLWrite_client is simply return dcb_write(dcb, queue);
The return codes are not the same of the code replaced, but they are not checked in the caller routines.

server/modules/protocol/mysql_client.c

@@ -433,7 +433,7 @@ static int gw_mysql_do_authentication(DCB *dcb, GWBUF *queue) {
 int
 gw_MySQLWrite_client(DCB *dcb, GWBUF *queue)
 {
-#if 0
+#if 1
 	return dcb_write(dcb, queue);
 #else
 int	w, saved_errno = 0;

server/modules/protocol/mysql_common.c

@@ -986,7 +986,7 @@ int gw_send_change_user_to_backend(char *dbname, char *user, uint8_t *passwd, My
 
 	rv = dcb->func.write(dcb, buffer);
 
-	if (rv < 0)
+	if (rv == 0)
 		return 0;
 	else
 		return 1;