Fix java lesson04 Formatter/Publisher reporting to Jaeger.

[smlobo]

• The difference between the java/lesson03 solution and lesson4 is the JaegerTracer is initilized before the Dropwizard server, in the latter.
• This results in the RemoteReporter-QueueProcessor (and FlushTimer) thread getting killed by the Dropwizard server when it starts later.
• Thus, Jaeger spans are not reported to port 6831 by the lesson04 Publisher/Formatter.
• Fix by reverting to the lesson03 pattern for startup.
• Explicitly calling close() on the JaegerTracer is not necessary since it registers a shutdownHook.

[smlobo]

Good question. The lesson03 README was slightly incorrect, and differed from the lesson03 source code. Updated this. No change to other READMEs seem necessary.