[8u] RFR 8246193: Possible NPE in ENC-PA-REP search in AS-REQ

[Zhengyu Gu]

Hi,

I would like to backport this to 8u for parity with Oracle 8u271.

Original patch did not apply cleanly. The only conflict was copyright 
line of KDC.java.

However, the new test (AlwaysEncPaReq.java) used new feature, introduced 
by JDK-8134577 from jdk9, which is not in jdk8u. Therefore, I 
implemented FakeNameService in test to replace file based DNS lookup 
mechanism in original test.

Original bug: https://bugs.openjdk.java.net/browse/JDK-8246193
Original patch: https://hg.openjdk.java.net/jdk/jdk/rev/7136c4d29901

8u webrev: http://cr.openjdk.java.net/~zgu/JDK-8246193-8u/webrev.00/

Test:
   jdk_security (includes new test)

Thanks,

-Zhengyu