Evaluate having ProxyFactoryFinderInterceptor clear the ProxyFactory ThreadLocal on request exit

On the way in, ProxyFactoryFinderInterceptor invokes Container.setProxyFactory, which in turn sets a ThreadLocal. On the way out there is no corresponding call that clears the ThreadLocal. Effect is the ProxyFactory leaks to the thread.

Need to confirm that clearing the TL on each request doesn't cause issues.