[WIP PATCH] Witness Server with CTDB integration

[Samuel Cabrero]

JFYI, at FOSDEM this weekend we're presenting a prototype Witness
implementation with CTDB integration. The code is available at:

https://gitlab.com/scabrero/samba/tree/witness-srv-v3

It's currently based atop the s3 DCE/RPC server, with impersonation
(thanks Metze) and async support, as well as Ralf's Persistent Handles
changes.

We're in the process of unifying (some components) of the s3 and s4
async DCE/RPC implementations and aim to submit something once Witness
is working atop that.

Cheers,

Samuel.