Block layer patches

- vhost-user-blk: Fix error handling during initialisation
- Add test cases for the vhost-user-blk export
- Fix leaked Transaction objects
- qcow2: Expose dirty bit in 'qemu-img info'

# gpg: Signature made Tue 18 May 2021 11:57:46 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:
  vhost-user-blk: Check that num-queues is supported by backend
  virtio: Fail if iommu_platform is requested, but unsupported
  vhost-user-blk: Get more feature flags from vhost device
  vhost-user-blk: Improve error reporting in realize
  vhost-user-blk: Don't reconnect during initialisation
  vhost-user-blk: Make sure to set Error on realize failure
  vhost-user-blk-test: test discard/write zeroes invalid inputs
  tests/qtest: add multi-queue test case to vhost-user-blk-test
  test: new qTest case to test the vhost-user-blk-server
  block/export: improve vu_blk_sect_range_ok()
  block: Fix Transaction leak in bdrv_reopen_multiple()
  block: Fix Transaction leak in bdrv_root_attach_child()
  qcow2: set bdi->is_dirty

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