Make java/nio/channels/Selector/RacyDeregister.java noisier and flush after prints

Apparently if a test times out in the jtreg harness it is less likely that anything written to System.err or System.out will be trapped and written to the .jtr file produced. If the test is made "noisier" and the outputs to the standard streams are flushed then, it should improve the odds of trapping this output which may help in diagnosing whether the test is timing out because it is hung or only because it is very slow.