adding <distributable> to webapp's web.xml causes ERROR on startup in default server profile

To reproduce, add <distributable> to a webapp's web.xml and deploy to a default server profile. You'll see the following exception thrown on the server console:

11:50:38,181 ERROR [JBossCacheManager] JBossCacheService to Tomcat clustering not found
java.lang.NoClassDefFoundError: org/jboss/cache/CacheException
[stacktrace]....

followed by ..

11:50:38,215 ERROR [TomcatDeployer] Failed to setup clustering, clustering disabled. Exception:
org.jboss.web.tomcat.tc5.session.ClusteringNotSupportedException: JBossCacheService to Tomcat clustering not found
[stacktrace]...

While the exception is true and the cluster is disabled at the end. It should only warn the user and not throw the exception.