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: Handle `EINVAL` fallocate return value
- qemu-img convert -n: Keep qcow2 v2 target sparse

# gpg: Signature made Tue 21 Jul 2020 16:45:28 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# 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:
  iotests: Test sparseness for qemu-img convert -n
  qcow2: Implement v2 zero writes with discard if possible
  file-posix: Handle `EINVAL` fallocate return value

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