Code review request, CR 7174244, NPE in Krb5ProxyImpl.getServerKeys()

[Xuelei Fan]

Hi Weijun,

Would you please review the fix for CR 7174244.
    http://cr.openjdk.java.net./~xuelei/7174244/webrev.00/

There are mainly two updates in the fix. One is to have
Krb5ProxyImpl.getServerKeys()  to check null return value of
Krb5Util.getServiceCreds(). The other one is to have cipher suite order
to be independent from HashMap implementation.  TreeSet is used to
replace ArrayList so that the cipher suites order are sorted automatically.

Thanks,
Xuelei