Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2017-04-03' into staging

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2017-04-03' into staging

Block patches for 2.9-rc3

# gpg: Signature made Mon 03 Apr 2017 16:29:49 BST
# gpg:                using RSA key 0xF407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2017-04-03:
  block/parallels: Avoid overflows
  iotests: Improve image-clear tests on non-aligned image
  qcow2: Discard unaligned tail when wiping image
  iotests: fix 097 when run with qcow
  qemu-io-cmds: Assert that global and nofile commands don't use ct->perms
  sheepdog: Fix blockdev-add
  nbd: Tidy up blockdev-add interface
  sockets: New helper socket_address_crumple()
  qapi-schema: SocketAddressFlat variants 'vsock' and 'fd'
  gluster: Prepare for SocketAddressFlat extension
  block: Document -drive problematic code and bugs
  io vnc sockets: Clean up SocketAddressKind switches
  char: Fix socket with "type": "vsock" address
  nbd sockets vnc: Mark problematic address family tests TODO
  block: add missed aio_context_acquire into release_drive

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