Before this patch for distributed queries, that requires cancellation
(simple select from multiple shards with limit, i.e. `select * from
remote('127.{2,3}', system.numbers) limit 100`) it is very easy to
trigger the situation when remote shard is in the middle of sending Data
block while the initiator already send Cancel and expecting some new
packet, but it will receive not new packet, but part of the Data block
that was in the middle of sending before cancellation, and this will
lead to some various errors, like:
- Unknown packet X from server Y
- Unexpected packet from server Y
- and a lot more...

Fix this, by correctly waiting for the pending packet before
cancellation.

It is not very easy to write a test, since localhost is too fast.

Also note, that it is not possible to get these errors with hedged
requests (use_hedged_requests=1) since handle fibers correctly.

But it had been disabled by default for 21.3 in ClickHouse#21534, while
async_socket_for_remote is enabled by default.