Merge remote-tracking branch 'remotes/jnsnow/tags/ide-pull-request' into staging

# gpg: Signature made Wed 13 Apr 2016 00:32:22 BST using RSA key ID AAFC390E
# gpg: Good signature from "John Snow (John Huston) <jsnow@redhat.com>"

* remotes/jnsnow/tags/ide-pull-request:
  ide: really restart pending and in-flight atapi dma
  ide: restart atapi dma by re-evaluating command packet
  ide: don't lose pending dma state
  xen: Fix IDE unplug

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