Merge tag 'pull-nbd-2021-12-22-v2' of https://src.openvz.org/scm/~vsementsov/qemu into staging
nbd: reconnect-on-open feature
v2: simple fix for mypy and pylint complains on patch 04
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* tag 'pull-nbd-2021-12-22-v2' of https://src.openvz.org/scm/~vsementsov/qemu:
iotests: add nbd-reconnect-on-open test
iotests.py: add qemu_io_popen()
iotests.py: add and use qemu_io_wrap_args()
iotests.py: add qemu_tool_popen()
nbd/client-connection: improve error message of cancelled attempt
nbd/client-connection: nbd_co_establish_connection(): return real error
nbd: allow reconnect on open, with corresponding new options
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>