added eventSetClasspath to set grails.server.factory

Burt,

I've been getting this error with functional tests in 2.3.x while testing a plugin I want to get working with Jetty:

| Environment set to test..... 
| Error No default container found. Please install a container plugin such as 'tomcat' first. 

It looks like the error is originating here: 
https://github.com/grails/grails-core/blob/master/grails-web/src/main/groovy/org/codehaus/groovy/grails/project/container/GrailsProjectRunner.groovy#L153

Ken