Tomcat is not reading /META-INF/context.xml because of the way we are configuring Tomcat at build time.
In server.xml, we overwrite the property deployXML to false, when this attribute should be set to true so that Tomcat can read in the context.xml file and properly place it in /conf/[engine]/[host]/[plugin-name].xml.
Note, previously it may have been disabled so that undeploying portlets would not leave /conf/[engine]/[host]/[plugin-name].xml in the conf folder. This was a bug in Tomcat that has been fixed. Tomcat, on undeploy, will remove this file as well.