Refactor `AbstractSimpleTransportTestCase` and `MockTransportService` to not use `Version.transportVersion` 
x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/transport/netty4/SimpleSecurityNetty4ServerTransportTests.java
assertThat(sslEngine.getNeedClientAuth(), is(true));
                assertThat(sslEngine.getWantClientAuth(), is(false));
            }
        }
        
        value = randomCapitalization(SslClientAuthenticationMode.NONE);
        settings = Settings.builder().put("xpack.security.transport.ssl.client_authentication", value).build();
        try (MockTransportService service = buildService("TS_NO_CLIENT_AUTH", Version.CURRENT, settings)) {
            TcpTransport originalTransport = (TcpTransport) service.getOriginalTransport();
            try (Transport.Connection connection2 = openConnection(serviceA, service.getLocalNode(), TestProfiles.LIGHT_PROFILE)) {
                sslEngine = getEngineFromAcceptedChannel(originalTransport, connection2);
                assertThat(sslEngine.getNeedClientAuth(), is(false));
                assertThat(sslEngine.getWantClientAuth(), is(false));
            }
        }
        
        value = randomCapitalization(SslClientAuthenticationMode.OPTIONAL);
        settings = Settings.builder().put("xpack.security.transport.ssl.client_authentication", value).build();
        try (MockTransportService service = buildService("TS_OPTIONAL_CLIENT_AUTH", Version.CURRENT, settings)) {
            TcpTransport originalTransport = (TcpTransport) service.getOriginalTransport();
            try (Transport.Connection connection2 = openConnection(serviceA, service.getLocalNode(), TestProfiles.LIGHT_PROFILE)) {
                sslEngine = getEngineFromAcceptedChannel(originalTransport, connection2);
                assertThat(sslEngine.getNeedClientAuth(), is(false));
                assertThat(sslEngine.getWantClientAuth(), is(true));
            }
        }
        
        value = randomCapitalization(SslClientAuthenticationMode.REQUIRED);
        settings = Settings.builder()
            .put("transport.profiles.client.port", "8000-9000")