Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-07-02' into staging

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-07-02' into staging

Block patches for 4.1-rc0:
- The stream job no longer relies on a fixed base node
- The rbd block driver can now accomodate growing formats like qcow2

# gpg: Signature made Tue 02 Jul 2019 02:56:06 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "[email protected]"
# gpg: Good signature from "Max Reitz <[email protected]>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2019-07-02:
  block/stream: introduce a bottom node
  block/stream: refactor stream_run: drop goto
  block: include base when checking image chain for block allocation
  block/rbd: increase dynamically the image size

Signed-off-by: Peter Maydell <[email protected]>