Block layer patches

# gpg: Signature made Tue 28 Feb 2017 20:35:32 GMT
# gpg:                using RSA key 0x7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (46 commits)
  block: Add Error parameter to bdrv_append()
  block: Add Error parameter to bdrv_set_backing_hd()
  block: Assertions for resize permission
  block: Assertions for write permissions
  block: Pass BdrvChild to bdrv_aligned_preadv/pwritev and copy-on-read
  tests: Remove FIXME comments
  nbd/server: Use real permissions for NBD exports
  migration/block: Use real permissions
  hmp: Request permissions in qemu-io
  commit: Add filter-node-name to block-commit
  mirror: Add filter-node-name to blockdev-mirror
  stream: Use real permissions in streaming block job
  mirror: Use real permissions in mirror/active commit block job
  blockjob: Factor out block_job_remove_all_bdrv()
  block: Allow backing file links in change_parent_backing_link()
  block: BdrvChildRole.attach/detach() callbacks
  block: Fix pending requests check in bdrv_append()
  backup: Use real permissions in backup block job
  commit: Use real permissions for HMP 'commit'
  commit: Use real permissions in commit block job
  ...

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