[BUG]Fix data_status sync issue

[charles-typ]

Describe the bug

In the directory server, there will be sync issues when a thread tries to delete a data block and another thread tries to read the the data blocks(vector).

[anuragkh]

A simple fix would be to switch the directory server threading model to non_blocking_server with a single serving thread and multiple IO threads. I can take care of this.