MXS-1203: Fix current command tracking with statement routing

When statement based routing was used, it was possible that the current
statement being executed wasn't properly updated. Readwritesplit requires
it to track whether a command will create a response.

server/modules/protocol/MySQL/MySQLClient/mysql_client.c

@@ -1399,6 +1399,10 @@ static int route_by_statement(MXS_SESSION* session, uint64_t capabilities, GWBUF
         if (packetbuf != NULL)
         {
             CHK_GWBUF(packetbuf);
+
+            MySQLProtocol* proto = session->client_dcb->protocol;
+            proto->current_command = (mysql_server_cmd_t)GWBUF_DATA(packetbuf)[4];
+
             /**
              * This means that buffer includes exactly one MySQL
              * statement.