Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-08-19' into staging

Block patches:
- preallocation=falloc/full support for LUKS
- Various minor fixes

# gpg: Signature made Mon 19 Aug 2019 16:36:45 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-2019-08-19:
  doc: Preallocation does not require writing zeroes
  iotests: Fix 141 when run with qed
  vpc: Do not return RAW from block_status
  vmdk: Make block_status recurse for flat extents
  vdi: Make block_status recurse for fixed images
  iotests: Full mirror to existing non-zero image
  iotests: Test convert -n to pre-filled image
  iotests: Convert to preallocated encrypted qcow2
  vhdx: Fix .bdrv_has_zero_init()
  vdi: Fix .bdrv_has_zero_init()
  qcow2: Fix .bdrv_has_zero_init()
  block: Use bdrv_has_zero_init_truncate()
  block: Implement .bdrv_has_zero_init_truncate()
  block: Add bdrv_has_zero_init_truncate()
  mirror: Fix bdrv_has_zero_init() use
  qemu-img: Fix bdrv_has_zero_init() use in convert
  LUKS: support preallocation

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