**Describe the bug**
`SYSTEM KILL` does not shutdown the server when run in a docker environment. I used https://hub.docker.com/r/yandex/clickhouse-server/ instructions to setup the docker.

**How to reproduce**
* ClickHouse server version 20.12.4 revision 54442.
```
myrotk@altinity-qa-cosmic3:~$ docker pull yandex/clickhouse-server
Using default tag: latest
latest: Pulling from yandex/clickhouse-server
da7391352a9b: Pull complete
14428a6d4bcd: Pull complete
2c2d948710f2: Pull complete
076cd2c6a81e: Pull complete
201ea6cda8c8: Pull complete
0d7b4e598027: Pull complete
0d86a58e3639: Pull complete
3b78a4fd0f92: Pull complete
86d65487f611: Pull complete
dc82dea7d6fe: Pull complete
Digest: sha256:8f669dafd35eb527210cc77973ed927734dff2c2cafd345823c8c99769124fd1
Status: Downloaded newer image for yandex/clickhouse-server:latest
docker.io/yandex/clickhouse-server:latest

myrotk@altinity-qa-cosmic3:~$ docker run -d --name some-clickhouse-server --ulimit nofile=262144:262144 yandex/clickhouse-server
35603911ec6c5737f069a019a60d03270cefe78e52c77d1bc6ff33a0548ae97e

myrotk@altinity-qa-cosmic3:~$ docker run -it --rm --link some-clickhouse-server:clickhouse-server yandex/clickhouse-client --host clickhouse-server
Unable to find image 'yandex/clickhouse-client:latest' locally
latest: Pulling from yandex/clickhouse-client
f22ccc0b8772: Pull complete
3cf8fb62ba5f: Pull complete
e80c964ece6a: Pull complete
6f064a173914: Pull complete
37a06aaf9ee5: Pull complete
Digest: sha256:504e18bed5162a20bbff6071ca1b7c7baca1380d2e2755e4d6bf4bac7e534531
Status: Downloaded newer image for yandex/clickhouse-client:latest
ClickHouse client version 20.12.4.5 (official build).
Connecting to clickhouse-server:9000 as user default.
Connected to ClickHouse server version 20.12.4 revision 54442.

35603911ec6c :) SYSTEM KILL

SYSTEM KILL

Query id: 0da8cfef-36c8-4de9-8c12-3e9175c5aed0

Ok.

0 rows in set. Elapsed: 0.002 sec.

35603911ec6c :)



{
    struct sigaction sa;
    memset(&sa, 0, sizeof(sa));
    sa.sa_sigaction = handler;
    sa.sa_flags = SA_SIGINFO;
#if defined(OS_DARWIN)
    sigemptyset(&sa.sa_mask);
    for (auto signal : signals)
        sigaddset(&sa.sa_mask, signal);
#else
    if (sigemptyset(&sa.sa_mask))
        throw Poco::Exception("Cannot set signal handler.");
    for (auto signal : signals)
        if (sigaddset(&sa.sa_mask, signal))
            throw Poco::Exception("Cannot set signal handler.");
#endif
    for (auto signal : signals)
        if (sigaction(signal, &sa, nullptr))
            throw Poco::Exception("Cannot set signal handler.");
    if (out_handled_signals)
        std::copy(signals.begin(), signals.end(), std::back_inserter(*out_handled_signals));
};
static void blockSignals(const std::vector<int> & signals)