Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

# gpg: Signature made Thu 31 Aug 2017 09:21:49 BST
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  qcow2: allocate cluster_cache/cluster_data on demand
  qemu-doc: Add UUID support in initiator name
  tests: migration/guestperf Python 2.6 argparse compatibility
  docker.py: Python 2.6 argparse compatibility
  scripts: add argparse module for Python 2.6 compatibility
  misc: Remove unused Error variables
  oslib-posix: Print errors before aborting on qemu_alloc_stack()
  throttle: Test the valid range of config values
  throttle: Make burst_length 64bit and add range checks
  throttle: Make LeakyBucket.avg and LeakyBucket.max integer types
  throttle: Remove throttle_fix_bucket() / throttle_unfix_bucket()
  throttle: Make throttle_is_valid() a bit less verbose
  throttle: Update the throttle_fix_bucket() documentation
  throttle: Fix wrong variable name in the header documentation
  nvme: Fix get/set number of queues feature, again

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