Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Thu Jul  2 10:10:39 2015 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request:
  block: remove redundant check before g_slist_find()
  block/nfs: limit maximum readahead size to 1MB
  block/iscsi: restore compatiblity with libiscsi 1.9.0
  iotests: Use event_wait in wait_ready
  qemu-iotests: Add test case for mirror with unmap
  qemu-iotests: Make block job methods common
  block: Remove bdrv_reset_dirty
  block: Fix dirty bitmap in bdrv_co_discard
  mirror: Do zero write on target if sectors not allocated
  qmp: Add optional bool "unmap" to drive-mirror
  block: Add bdrv_get_block_status_above
  timer: Use a single definition of NSEC_PER_SEC for the whole codebase
  timer: Move NANOSECONDS_PER_SECONDS to timer.h
  blockdev: no need to drain+flush in hmp_drive_del
  qapi: Rename 'dirty-bitmap' mode to 'incremental'
  qcow2: Handle EAGAIN returned from update_refcount
  block/iscsi: add support for request timeouts

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