Update SaslClientCallbackHandler.java

Add default constructor
Changed declaration of client_password and client_name to public from public final.
Added getters/setters for client_password and client_name for supporting the instantiation of instances via new default constructor.
Merge pull request #185 from mwigglesworth-redhat/3.4

Update SaslClientCallbackHandler.java : Support for callbackhandler to be utilized directly by jgroups.xml <SASL/> block configuration.