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

Block layer patches

# gpg: Signature made Tue 26 Sep 2017 14:52:32 BST
# gpg:                using RSA key 0x7F09B272C88F2FD6
# 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: (24 commits)
  block/qcow2-bitmap: fix use of uninitialized pointer
  qemu-iotests: add shrinking image test
  qcow2: add shrink image support
  qcow2: add qcow2_cache_discard
  qemu-img: add --shrink flag for resize
  iotests: fix 181: enable postcopy-ram capability on target
  qemu-iotests: Test change-backing-file command
  block: Fix permissions after bdrv_reopen()
  block: reopen: Queue children after their parents
  block: Base permissions on rw state after reopen
  block: Add reopen queue to bdrv_check_perm()
  block: Add reopen_queue to bdrv_child_perm()
  qemu-io: Drop write permissions before read-only reopen
  block: Clean up some bad code in the vvfat driver
  block/throttle-groups.c: allocate RestartData on the heap
  throttle: Assert that bkt->max is valid in throttle_compute_wait()
  iotests: Print full path of bad output if mismatch
  iotests: use virtio aliases for 067
  iotests: use -ccw on s390x for 051
  iotests: use -ccw on s390x for 040, 139, and 182
  ...

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