Authenticates the caller using the principal and credentials in the
Infocation if thre is a security manager and an invcocation method.
// Get Principal and credentials
Principal principal = SecurityActions.getPrincipal();
if (principal != null) invocation.getMetaData().addMetaData("security", "principal", principal);
Object credential = SecurityActions.getCredential();
if (credential != null) invocation.getMetaData().addMetaData("security", "credential", credential);
return invocation.invokeNext();