function perf_test()
{
    time yes '127.1:8123/?wait_end_of_query=1' | head -n10000 | xargs -P10000 curl -s -d 'select 1' | grep -x -c 1
}
function server()
{
    local limit=$1 && shift
    clickhouse-server "$@" -- --max_server_memory_usage=$limit
}

perf_test:

- before this patch with 1G  limit: succeed only ~800  queries
- after  this patch with 1G  limit: succeed      ~8000 queries

- before this patch with 10G limit: succeed only ~3000  queries
- after  this patch with 10G limit: succeed      ~10000 queries

Fixes: ClickHouse#11153

w/o the patch the test fails with, since it succeed only 512 queries.

Actually there were two issues:
- missing \n, so it picked the wrong query anway
- no unique identifier, hence it may works incorrectly (and actually,
  event clickhouse-test script executes 'SELECT 1' query)