iotests: Test NBD client reconnection

The test for an NBD client. The NBD server is disconnected after the
client write request. The NBD client should reconnect and complete
the write operation.

Suggested-by: Denis V. Lunev <den@openvz.org>
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Message-Id: <1573529976-815699-1-git-send-email-andrey.shinkevich@virtuozzo.com>
5 files changed