AS7-6346 Use the correct classloader during creation of EJBClientContext

The commit here fixes the issue that was discovered while working on a quickstart as part of https://issues.jboss.org/browse/AS7-6346. The EJBClientContext creation wasn't using the correct classloader and furthermore the default META-INF/services of the auto-added org.jboss.ejb.client  module dependency wasn't visible to the deployment. This PR fixes these issues.