void validateRegionUsingRegionhelper(RegionConfiguration configuration, Region region) {
    RegionHelper.validateRegion((Cache) getCache(), configuration, region);
  }
For peer-to-peer the backing cache *is* what's embedded in tomcat so it's always available

@return boolean indicating whether a backing cache is available
extensions/geode-modules/src/main/java/org/apache/geode/modules/session/catalina/PeerToPeerSessionCache.java