The test was not keeping any strong reference on the loggers it created allowing for them to be garbage collected too early.
Reviewed-by: mchung, chegar
8021003: java/util/logging/Logger/getGlobal/TestGetGlobalConcurrent.java fails intermittently
8019945: test/java/util/logging/LogManagerInstanceTest.java failing intermittently
This fix untangles the class initialization of Logger and LogManager, and also cleans up the relationship between LogManager, LoggerContext, and Logger, which were at the root cause of some intermittent test failures.
Reviewed-by: mchung, martin, plevart
