Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches for 2.6.0-rc3

# gpg: Signature made Fri 15 Apr 2016 17:02:23 BST using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream:
  nbd: Don't kill server on client that doesn't request TLS
  nbd: fix assert() on qemu-nbd stop
  nbd: Don't fail handshake on NBD_OPT_LIST descriptions
  qemu-iotests: 041: More robust assertion on quorum node
  qemu-iotests: place valgrind log file in scratch dir
  qemu-iotests: tests: do not set unused tmp variable
  qemu-iotests: common.rc: drop unused _do()
  qemu-iotests: drop unused _within_tolerance() filter
  Fix pflash migration
  block: Don't ignore flags in blk_{,co,aio}_write_zeroes()
  block/vpc: update comments to be compliant w/coding guidelines
  block/vpc: set errp in vpc_open
  block/vpc: make checks on max table size a bit more lax
  block/vpc: Use the correct max sector count for VHD images
  block/vpc: use current_size field for XenConverter VHD images
  vpc: use current_size field for XenServer VHD images
  block/vpc: set errp in vpc_create
  block: Fix blk_aio_write_zeroes()
  qemu-io: Support 'aio_write -z'

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>