Update for compatibility with 2.4

[selera]

It needs ApplicationHolder replaced with Holders

In src/groovy/grails/ldap/server/TransientGrailsLdapServer.groovy

Around line 63, replace with:

        def baseConfigDirPath = (Holders.grailsApplication.warDeployed) ? Holders.grailsApplication.parentContext.getResource("WEB-INF/grails-app/ldap-servers").file.path : "grails-app/ldap-servers"

Also fix the import to be:

import grails.util.Holders

[jshickey]

This is a blocker for adopting Grails 2.4. Any chance of a new version being published with this fix?