Fix for missing property `mergedConfig`

Hi Josh,

Here's the fix for the issue i mentioned on the mailing list:

> When starting my app in dev mode, everything is fine.  When running
from the WAR, I get the following Exception:

    org.springframework.beans.factory.access.BootstrapException: Error executing bootstraps; nested exception is groovy.lang.MissingPropertyException: No such property: mergedConfig for class: org.codehaus.groovy.grails.commons.DefaultGrailsApplication
    ....
    groovy.lang.MissingPropertyException: No such property: mergedConfig for class: org.codehaus.groovy.grails.commons.DefaultGrailsApplication
    ....

Alex