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:

- file-posix: Ignore unlock failure instead of crashing
- gluster: Limit the transfer size to 512 MiB
- stream: Fix backing chain freezing
- qemu-img: Enable BDRV_REQ_MAY_UNMAP for zero writes in convert
- iotests fixes

# gpg: Signature made Tue 02 Apr 2019 13:47:43 BST
# gpg:                using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  tests/qemu-iotests/235: Allow fallback to tcg
  block: test block-stream with a base node that is used by block-commit
  block: freeze the backing chain earlier in stream_start()
  block: continue until base is found in bdrv_freeze_backing_chain() et al
  block/file-posix: do not fail on unlock bytes
  tests/qemu-iotests: Remove redundant COPYING file
  block/gluster: limit the transfer size to 512 MiB
  qemu-img: Enable BDRV_REQ_MAY_UNMAP in convert
  iotests: Fix test 200 on s390x without virtio-pci

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