Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Tue 12 Apr 2016 09:29:54 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <[email protected]>"
# gpg:                 aka "Stefan Hajnoczi <[email protected]>"

* remotes/stefanha/tags/block-pull-request:
  MAINTAINERS: Add Fam Zheng as a co-maintainer of block I/O path
  mirror: Replace bdrv_drain(bs) with bdrv_co_drain(bs)
  block: Fix bdrv_drain in coroutine

Signed-off-by: Peter Maydell <[email protected]>