JGRP-1838 Separate CallbackHandler depending on mode of operation
JGRP-1839 Wrap calls to saslClient.evaluateChallenge in a PrivilegedAction for GSSAPI
Merge pull request #142 from tristantarrant/JGRP-1838/callbacks/master

JGRP-1838 & JGRP-1839 SASL fixes