Meta server: fix write lease expiry logic: never expire write leases if chunk allocation is in flight, even (well, especially) if chunk isn't present in chunk map, as with the initial (version 1) allocation the chunk will only be added when allocation finishes successfully. The bug had only effect on initial chunk allocation and caused spurious chunk allocation failures and retries on the client when lease timer run.
Merge branch 'master' into topic/tiered_storage