CAS-1403: Buffer limit exceeded writing object of type: javax.security.auth.login.FailedLoginException

To fix the problem, according to Marvin's advice (https://groups.google.com/forum/?fromgroups#!topic/jasig-cas-dev/DkTXOWi2Q-Q), I replaced the ```Exception``` object used for failures by a ```Class<? extends Exception>``` object.
I also updated the serialization test.