FETCH COLLAPSE : Change the fetch-lock collapse to collapse ALL fetches, including...

FETCH COLLAPSE : Change the fetch-lock collapse to collapse ALL fetches, including fetch-locks into a single command in flight per record. Also add a tunable to enable/disable this optimization for hot records

Conflicts:
	server/ctdb_tunables.c

Cherry-pick-from: eafd7bbaaa5931546a96c8beae3cf9a39a49c925