Clean up WebSocket tests

* Remove recursive send/receive.

* Correct the CountDownLatch count numbers. Mixes between Client and
Server Encoder/Decoders and rely on multiple messages being echoed.

* GlassFish is more sensible to double slashes in WS URL's. Remove
the extra forward slashes.

* Pr spec you can only register a single Message Handler pr type. Change
to store Message in static to verify content.