Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2019-04-08' into staging

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2019-04-08' into staging

nbd patches for 2019-04-08

- Fix minor issues in recent alignment patches

# gpg: Signature made Mon 08 Apr 2019 19:53:48 BST
# gpg:                using RSA key A7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg:                 aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [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-2019-04-08:
  nbd/client: Fix error message for server with unusable sizing
  nbd/server: Don't fail NBD_OPT_INFO for byte-aligned sources
  nbd/server: Trace client noncompliance on unaligned requests
  nbd/server: Fix blockstatus trace

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