Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2018-05-04' into staging

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2018-05-04' into staging

nbd patches for 2018-05-04

- Vladimir Sementsov-Ogievskiy: 0/2 fix coverity bugs
- Eric Blake: nbd/client: Fix error messages during NBD_INFO_BLOCK_SIZE
- Eric Blake: nbd/client: Relax handling of large NBD_CMD_BLOCK_STATUS reply

# gpg: Signature made Fri 04 May 2018 14:25:55 BST
# gpg:                using RSA key A7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>"
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>"
# gpg:                 aka "[jpeg image of size 6874]"
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2  F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2018-05-04:
  nbd/client: Relax handling of large NBD_CMD_BLOCK_STATUS reply
  nbd/client: Fix error messages during NBD_INFO_BLOCK_SIZE
  migration/block-dirty-bitmap: fix memory leak in dirty_bitmap_load_bits
  nbd/client: fix nbd_negotiate_simple_meta_context

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