Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2020-07-06' into staging

Block patches for 5.1:
- LUKS keyslot amendment
  (+ patches to make the iotests pass on non-Linux systems, and to keep
     the tests passing for qcow v1, and to skip LUKS tests (including
     qcow2 LUKS) when the built qemu does not support it)
- Refactoring in the block layer: Drop the basically unnecessary
  unallocated_blocks_are_zero field from BlockDriverInfo
- Fix qcow2 preallocation when the image size is not a multiple of the
  cluster size
- Fix in block-copy code

# gpg: Signature made Mon 06 Jul 2020 11:02:53 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2020-07-06: (31 commits)
  qed: Simplify backing reads
  block: drop unallocated_blocks_are_zero
  block/vhdx: drop unallocated_blocks_are_zero
  block/file-posix: drop unallocated_blocks_are_zero
  block/iscsi: drop unallocated_blocks_are_zero
  block/crypto: drop unallocated_blocks_are_zero
  block/vpc: return ZERO block-status when appropriate
  block/vdi: return ZERO block-status when appropriate
  block: inline bdrv_unallocated_blocks_are_zero()
  qemu-img: convert: don't use unallocated_blocks_are_zero
  iotests: add tests for blockdev-amend
  block/qcow2: implement blockdev-amend
  block/crypto: implement blockdev-amend
  block/core: add generic infrastructure for x-blockdev-amend qmp command
  iotests: qemu-img tests for luks key management
  block/qcow2: extend qemu-img amend interface with crypto options
  block/crypto: implement the encryption key management
  block/crypto: rename two functions
  block/amend: refactor qcow2 amend options
  block/amend: separate amend and create options for qemu-img
  ...

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