In current DNE implementation, when creating a striped directory. In execution phase, the master MDT will only pack the remote updates inside the RPC, and these updates will not be executed until top_trans_stop() sends these updates to remote MDT. If these remote updates fails, for example ENOSPC for writing update log, but local updates succeeds, then we need rollback those local updates (or do better job during declaration?), otherwise the namespace space might be inconsistency.

This can be reproduced by the test case in http://review.whamcloud.com/16677