shutdown/redeploy of workbench results in lock exception for query repository

When using the tomcat manager to shut down the workbench application, undeploy it, and redeploy, an error appears when trying to access the workbench.

trace:

At first glance, it looks as if the workbench does not properly shut down the repository it uses for storing queries. Possible fix is a runtime shutdownhook, or switching to the new RepositoryProvider class (which takes care of shutting down cleanly for you).