clickhouse-keeper: correctly handle closed client connection

This will avoid noisy message like:

    DB::Exception: Cannot read all data. Bytes read: 0. Bytes expected: 4.

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

src/Server/KeeperTCPHandler.cpp

@@ -415,6 +415,12 @@ void KeeperTCPHandler::runImpl()
             log_long_operation("Polling socket");
             if (result.has_requests && !close_received)
             {
+                if (in->eof())
+                {
+                    LOG_DEBUG(log, "Client closed connection, session id #{}", session_id);
+                    break;
+                }
+
                 auto [received_op, received_xid] = receiveRequest();
                 packageReceived();
                 log_long_operation("Receiving request");