[AS7-6730] New test case to test specifying an identity to run as from an unsecured EJB.
[AS7-6730] Modification to the security interceptors so that the push of the SecurityContext is separated from the authentication step.

Also wrap the Remoting Connection in the Credential so that it can reach the LoginModule instead of relyign on the ThreadLocal, this
means that the Credential will remain available until any intermediate bean sets an alternative.