Install JvmRouteValve into context pipeline by default in JBossCacheManager

Following JBAS-8007, mod_cluster will start after jbossweb. By default, mod_cluster uses an auto-generated jvmRoute. However, any context deployed on server startup will not have the appropriate JvmRouteValve installed in its pipeline, since their engine does not yet have a jvmRoute.
To fix this, we should install the JvmRouteValve by default. Also, JvmRouteValve should no longer throw an exception if no jvmRoute is defined - and instead fall through.