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

Block layer patches:

- Active mirror (blockdev-mirror copy-mode=write-blocking)
- bdrv_drain_*() fixes and test cases
- Fix crash with scsi-hd and drive_del

# gpg: Signature made Mon 18 Jun 2018 17:44:10 BST
# gpg:                using RSA key 7F09B272C88F2FD6
# 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: (35 commits)
  iotests: Add test for active mirroring
  block/mirror: Add copy mode QAPI interface
  block/mirror: Add active mirroring
  job: Add job_progress_increase_remaining()
  block/mirror: Add MirrorBDSOpaque
  block/dirty-bitmap: Add bdrv_dirty_iter_next_area
  test-hbitmap: Add non-advancing iter_next tests
  hbitmap: Add @advance param to hbitmap_iter_next()
  block: Generalize should_update_child() rule
  block/mirror: Use source as a BdrvChild
  block/mirror: Wait for in-flight op conflicts
  block/mirror: Use CoQueue to wait on in-flight ops
  block/mirror: Convert to coroutines
  block/mirror: Pull out mirror_perform()
  block: fix QEMU crash with scsi-hd and drive_del
  test-bdrv-drain: Test graph changes in drain_all section
  block: Allow graph changes in bdrv_drain_all_begin/end sections
  block: ignore_bds_parents parameter for drain functions
  block: Move bdrv_drain_all_begin() out of coroutine context
  block: Allow AIO_WAIT_WHILE with NULL ctx
  ...

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