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

# gpg: Signature made Wed 11 Nov 2015 16:03:19 GMT using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"

* remotes/kevin/tags/for-upstream: (41 commits)
  iotests: Check for quorum support in test 139
  qcow2: Fix qcow2_get_cluster_offset() for zero clusters
  iotests: Add tests for the x-blockdev-del command
  block: Add 'x-blockdev-del' QMP command
  block: Add blk_get_refcnt()
  mirror: block all operations on the target image during the job
  qemu-iotests: fix -valgrind option for check
  qemu-iotests: fix cleanup of background processes
  qemu-io: Correct error messages
  qemu-io: Check for trailing chars
  qemu-io: fix cvtnum lval types
  block: test 'blockdev-snapshot' using a file BDS as the overlay
  block: Remove inner quotation marks in iotest 085
  block: Disallow snapshots if the overlay doesn't support backing files
  throttle: Use bs->throttle_state instead of bs->io_limits_enabled
  throttle: Check for pending requests in throttle_group_unregister_bs()
  qemu-img: add check for zero-length job len
  qcow2: avoid misaligned 64bit bswap
  qemu-iotests: Test the reopening of overlay_bs in 'block-commit'
  commit: reopen overlay_bs before base
  ...

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