Fix flaky test_keeper_snapshots

[antonio2368]

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• Not for changelog (changelog entry is not required)

2023-04-04 22:35:38 [ 6903 ] DEBUG : Sending request(xid=None): Connect(protocol_version=0, last_zxid_seen=0, time_out=30000, session_id=0, passwd=b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00', read_only=None) (connection.py:312, _submit)
2023-04-04 22:35:38 [ 6903 ] INFO : Zookeeper connection established, state: CONNECTED (client.py:532, _session_callback)
2023-04-04 22:35:38 [ 6903 ] WARNING : Connection dropped: socket connection broken (connection.py:622, _connect_attempt)

It connected, but ZK clients don't support rejection in handshake we send if server is not active so Keeper just drops the connection while ZK thinks everything is okay.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

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[tavplubix]

Integration tests (asan) [1/6] - #43084
Integration tests flaky check (asan) - OK