javax.websocket.Session#isSecure() is always false

When a client initiates a secure session to a "wss" WebSocket server endpoint, the session#isSecure() method always returns false, although it's in fact secure.

The server side counterpart is working fine. (Wildfly 11, it's Tyrus, too).

I am initiating the SSL context with:
```
SslEngineConfigurator sslEngineConfigurator = new SslEngineConfigurator(getSSLContext());
client.getProperties().put(ClientProperties.SSL_ENGINE_CONFIGURATOR, sslEngineConfigurator);
```