SimpleProvisionMetrics ThreadLocal leak on Tomcat undeploy

[cristiancalugaru]

When undeploying a web app using ProvisionDebugModule, Tomcat will complain about a possible memory leak related to a thread local variable:

The web application [xxx] created a ThreadLocal with key of type [java.lang.ThreadLocal](value [java.lang.ThreadLocal@19b7a0b3]) and a value of type [com.netflix.governator.SimpleProvisionMetrics.Data](value [com.netflix.governator.SimpleProvisionMetrics$Data@47c13c28]) but failed to remove it when the web application was stopped.

This might be a similar issue with Netflix/Hystrix#320 and Netflix/Hystrix#816.
A workaround for now is not to use the ProvisionDebugModule.