- Drop the code from SSO (I didn't know StandardSession.expire was already setting the context CL.
- Add bind/unbind to StandardSession.expire instead (and only do it if the classloader actually changes).
- See later if the bind/unbind code can be moved to StandardContext, but all uses seem slightly different.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1560363 13f79535-47bb-0310-9956-ffa450edef68