Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-02-02-v2' into staging

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-02-02-v2' into staging

nbd patches for 2021-02-02

- more cleanup from iotest python conversion
- progress towards consistent use of signed 64-bit types through block layer
- fix some crashes related to NBD reconnect

# gpg: Signature made Wed 03 Feb 2021 14:20:01 GMT
# gpg:                using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# 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-2021-02-02-v2:
  nbd: make nbd_read* return -EIO on error
  block/nbd: only enter connection coroutine if it's present
  block/nbd: only detach existing iochannel from aio_context
  block/io: use int64_t bytes in copy_range
  block/io: support int64_t bytes in read/write wrappers
  block/io: support int64_t bytes in bdrv_co_p{read,write}v_part()
  block/io: support int64_t bytes in bdrv_aligned_preadv()
  block/io: support int64_t bytes in bdrv_co_do_copy_on_readv()
  block/io: support int64_t bytes in bdrv_aligned_pwritev()
  block/io: support int64_t bytes in bdrv_co_do_pwrite_zeroes()
  block/io: use int64_t bytes in driver wrappers
  block: use int64_t as bytes type in tracked requests
  block/io: improve bdrv_check_request: check qiov too
  block/throttle-groups: throttle_group_co_io_limits_intercept(): 64bit bytes
  block/io: bdrv_pad_request(): support qemu_iovec_init_extended failure
  block/io: refactor bdrv_pad_request(): move bdrv_pad_request() up
  block: fix theoretical overflow in bdrv_init_padding()
  util/iov: make qemu_iovec_init_extended() honest
  block: refactor bdrv_check_request: add errp
  iotests: Fix expected whitespace for 185

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