Merge remote-tracking branch 'mreitz/tags/pull-block-for-kevin-2015-11-11' into queue...

Block patches from 2015-10-26 until 2015-11-11.

# gpg: Signature made Wed Nov 11 17:00:50 2015 CET using RSA key ID E838ACAD
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"

* mreitz/tags/pull-block-for-kevin-2015-11-11:
  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

Signed-off-by: Kevin Wolf <kwolf@redhat.com>