Record Fetch Collapse: Collapse multiple fetch request into one single request.

Record Fetch Collapse: Collapse multiple fetch request into one single request.

When multiple clients fetch the same record concurrently, send only one single
fetch across the network and deferr all other fetches locally.
This improves performance for hot records and reduces cpu load on ctdb.

Conflicts:
	server/ctdb_ltdb_server.c

Cherry-pick-from: 82d6946ad8b3348e8b9d3d971f24925ade02d1be