MicroProfileHealthDefaultEmpty*HTTPEndpointTestCase manual mode test intermittent failures

MicroProfileHealthDefaultEmpty*HTTPEndpointTestCase manualmode tests intermittently fail with the following exception:
```
java.util.concurrent.ExecutionException: javax.json.stream.JsonParsingException: JsonParser#getObject() or JsonParser#getObjectStream() is valid only for START_OBJECT parser state. But current parser state is START_ARRAY
```

This is caused by not yet started MP Health subsystem and thus the request being handled by the original Health subsystem HTTP handler which responds with JSON array. The handler is overridden in the Service#start method.