[sheepdog] [sheepdog/sheepdog] 4adf02: sheep: disable async ledger update for VID recycli...

[Hitoshi Mitake]

  Branch: refs/heads/async-ledger
  Home:   https://github.com/sheepdog/sheepdog
  Commit: 4adf0267e8e2fa23f79ada99c83a28131c05bad6
      https://github.com/sheepdog/sheepdog/commit/4adf0267e8e2fa23f79ada99c83a28131c05bad6
  Author: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
  Date:   2016-09-30 (Fri, 30 Sep 2016)

  Changed paths:
    M sheep/gateway.c

  Log Message:
  -----------
  sheep: disable async ledger update for VID recycling mode

The async ledger update can cause data loss because the process of
decrementing reference count can be delayed and the target VID can be
used for newly created VDIs. This commit forbids the async update if
the cluster is formatted with VID recycling mode.

Fixes https://github.com/sheepdog/sheepdog/issues/315

Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>