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

Block layer patches

# gpg: Signature made Wed 06 Sep 2017 14:44:41 BST
# gpg:                using RSA key 0x7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  qcow2: move qcow2_store_persistent_dirty_bitmaps() before cache flushing
  qemu-iotests: add 184 for throttle filter driver
  block: add throttle block filter driver
  block: convert ThrottleGroup to object with QOM
  block: tidy ThrottleGroupMember initializations
  block: add aio_context field in ThrottleGroupMember
  block: move ThrottleGroup membership to ThrottleGroupMember
  block: document semantics of bdrv_co_preadv|pwritev
  qcow: Check failure of bdrv_getlength() and bdrv_truncate()
  qcow: Change signature of get_cluster_offset()
  block: add default implementations for bdrv_co_get_block_status()
  block: remove bdrv_truncate callback in blkdebug
  block: remove unused bdrv_media_changed
  block: pass bdrv_* methods to bs->file by default in block filters

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