Merge remote-tracking branch 'stefanha/block' into staging

# By Paolo Bonzini (17) and others
# Via Stefan Hajnoczi
* stefanha/block: (48 commits)
  qemu-iotests: filter QEMU monitor \r\n
  aio: make aio_poll(ctx, true) block with no fds
  block: clean up bdrv_drain_all() throttling comments
  qcow2: use start_of_cluster() and offset_into_cluster() everywhere
  qemu-img: decrease progress update interval on convert
  qemu-img: round down request length to an aligned sector
  qemu-img: dynamically adjust iobuffer size during convert
  block/iscsi: set bs->bl.opt_transfer_length
  block: add opt_transfer_length to BlockLimits
  block/iscsi: set bdi->cluster_size
  qemu-img: fix usage instruction for qemu-img convert
  qemu-img: add support for skipping zeroes in input during convert
  qemu-nbd: add doc for option -f
  qemu-iotests: add test for snapshot in qemu-img convert
  qemu-img: add -l for snapshot in convert
  qemu-iotests: add 058 internal snapshot export with qemu-nbd case
  qemu-nbd: support internal snapshot export
  snapshot: distinguish id and name in load_tmp
  qemu-iotests: Split qcow2 only cases in 048
  qemu-iotests: Clean up spaces in usage output
  ...

Message-id: 1386347807-27359-1-git-send-email-stefanha@redhat.com
Signed-off-by: Anthony Liguori <aliguori@amazon.com>