I get NPE in my Tomcat 6.0.35 when I try to access the servlet.
(GridStore Line 56)

Both (CacheManagerHolder.cacheContainer and CacheManagerHolder.dataCacheName) are null, because the InitServlet wasn't started or the init(..) wasn't processed.

I'd suggest to rewrite the InitServlet as ServletContextListener to use the
contextInit(..) and contextDestroyed(..) for these CacheManagerHolder init and shutdown stuff.