thread safety problem in uimaj-core code causing occasional hang

The class AnalysisEngineManagementImpl (which implements JMX instrumentation) uses a static set to remember what names have been used for "root" MBeans. Access to this set is not synchronized, so it's possible for two threads to try and simultaneously update this set. Check for other static sets/maps with this problem, too. Either convert this to a synchronized access, or use one of the concurrent maps/sets.