Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2019-02-11' into staging

nbd patches for 2019-02-11

- Add qcow2 bitmap details to 'qemu-img info'

# gpg: Signature made Mon 11 Feb 2019 20:38:32 GMT
# gpg:                using RSA key A7A16B4A2527436A
# gpg: Good signature from "Eric Blake <[email protected]>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <[email protected]>" [full]
# gpg:                 aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2019-02-11:
  qcow2: list of bitmaps new test 242
  qcow2: Add list of bitmaps to ImageInfoSpecificQCow2
  bdrv_query_image_info Error parameter added
  nbd/server: Kill pointless shadowed variable

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