Merge remote-tracking branch 'remotes/berrange/tags/pull-qio-2017-07-18-1' into staging

Merge I/O 2017/07/18 v1

# gpg: Signature made Tue 18 Jul 2017 11:31:53 BST
# gpg:                using RSA key 0xBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>"
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/pull-qio-2017-07-18-1:
  io: simplify qio_channel_attach_aio_context

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