Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2018-01-26' into staging

nbd patches for 2018-01-26

- Vladimir Sementsov-Ogievskiy - nbd export qmp interface
- Eric Blake - hmp: Add nbd_server_remove to mirror QMP command
- Edgar Kaziakhmedov - nbd: implement bdrv_get_info callback

# gpg: Signature made Fri 26 Jan 2018 16:02:34 GMT
# gpg:                using RSA key 0xA7A16B4A2527436A
# 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-2018-01-26:
  nbd: implement bdrv_get_info callback
  hmp: Add nbd_server_remove to mirror QMP command
  iotest 205: new test for qmp nbd-server-remove
  iotests: implement QemuIoInteractive class
  iotest 147: add cases to test new @name parameter of nbd-server-add
  qapi: add nbd-server-remove
  hmp: Add name parameter to nbd_server_add
  qapi: add name parameter to nbd-server-add

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