Wrap the MFA authentication object to include the entire chain

[mmoayyed]

The constructed authentication object that is placed into the final MFA-enabled TGT needs to not depend on a particular authentication object in the chain, but rather, should wrap the entire chain inside it.

CF. https://github.com/Unicon/cas-mfa/blob/master/cas-mfa-java/src/main/java/net/unicon/cas/mfa/authentication/principal/MultiFactorCredentials.java#L98

This is to support the usecase of remembering and fulfilling all authentication methods (which there may be multiples of) on validation responses.