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

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

Block layer patches:

- Generic background jobs
- qemu-iotests fixes for NFS and the 'migration' group
- sheepdog: Minor code simplification

# gpg: Signature made Wed 23 May 2018 13:33:49 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: (46 commits)
  qemu-iotests: Test job-* with block jobs
  iotests: Move qmp_to_opts() to VM
  blockjob: Remove BlockJob.driver
  job: Add query-jobs QMP command
  job: Add lifecycle QMP commands
  job: Add JOB_STATUS_CHANGE QMP event
  job: Introduce qapi/job.json
  job: Move progress fields to Job
  job: Add job_transition_to_ready()
  job: Add job_is_ready()
  job: Add job_dismiss()
  job: Add job_yield()
  block: Cancel job in bdrv_close_all() callers
  job: Move completion and cancellation to Job
  job: Move transactions to Job
  job: Switch transactions to JobTxn
  job: Move job_finish_sync() to Job
  job: Move .complete callback to Job
  job: Add job_drain()
  job: Convert block_job_cancel_async() to Job
  ...

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