Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2019-08-15' into staging

nbd patches for 2019-08-15

- Addition of InetSocketAddress keep-alive
- Addition of BDRV_REQ_PREFETCH for more efficient copy-on-read
- Initial refactoring in preparation of NBD reconnect

# gpg: Signature made Thu 15 Aug 2019 19:28:41 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-2019-08-15:
  block/nbd: refactor nbd connection parameters
  block/nbd: add cmdline and qapi parameter reconnect-delay
  block/nbd: move from quit to state
  block/nbd: use non-blocking io channel for nbd negotiation
  block/nbd: split connection_co start out of nbd_client_connect
  nbd: improve CMD_CACHE: use BDRV_REQ_PREFETCH
  block/stream: use BDRV_REQ_PREFETCH
  block: implement BDRV_REQ_PREFETCH
  qapi: Add InetSocketAddress member keep-alive

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

diff --cc block/io.c
Simple merge

diff --cc block/nbd.c
Simple merge

diff --cc include/block/block.h
Simple merge

diff --cc nbd/client.c
Simple merge

diff --cc nbd/server.c
Simple merge