I created _Events.groovy in script directory then added code below:
_Events.groovy
eventConfigureTomcat = {tomcat -> println \"Tomcat.......................
It appears that you can update the Tomcat plugin in Grails 2.3 to:
build ":tomcat:7.0.55"
This includes the fix for the jira issue that @chubbsondubs linked above. It also seems to be fixed in the tomcat plugin 8.0.14.