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

Mirror block job fixes for 2.6.0-rc4

# gpg: Signature made Fri 22 Apr 2016 15:46:41 BST using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream:
  mirror: Workaround for unexpected iohandler events during completion
  aio-posix: Skip external nodes in aio_dispatch
  virtio: Mark host notifiers as external
  event-notifier: Add "is_external" parameter
  iohandler: Introduce iohandler_get_aio_context

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