#8 Improve exception stacktraces in RadiusLoginModule

[Anonymous]

Currently, in the login() method, if you get an
UnsupportedCallbackException when this.callbackHandler.handle
(callbacks); runs, the user has no idea what the real cause was, because
the stacktrace for the UnsupportedCallbackException is lost.

This patch adds the UnsupportedCallbackException to the "Caused by"
clause, meaning it will be reported in the stacktrace.

Nathan Robertson (nathanr at nathanr dot net)

[Nobody/Anonymous]

Add UnsupportedCallbackException to the "Caused By" clause in a LoginException stacktrace