Distributed session manager reports HttpSession.getLastAccessedTime() incorrectly.

Currently, the distributed session manager updates the last accessed timestamp of a session at the end of a given request.  This is not correct.  According to §7.6 of the servlet specification:

The getLastAccessedTime method of the HttpSession interface allows a servlet to
determine the last time the session was accessed before the current request. The
session is considered to be accessed when a request that is part of the session is first handled by the servlet container.