JDK 9 RFR of JDK-8079769: tools/pack200/PackTestZip64.java may timeout at preparing the large test file

[Amy Lu]

Please review the fix for test issue: tools/pack200/PackTestZip64.java 
may timeout at preparing the large test file

This test tries to create a big jar file for testing by adding a large 
number (Short.MAX_VALUE * 2 + 2) of small files to the golden jar 
(golden.jar). This prepare work is i/o sensitive and may take long thus 
may timeout (depending on the run timeout settings), especially when 
many tests run in concurrency.

To make the test more stable, without losing test coverage, this fix makes:
* PackTestZip64.java tests on the golden.jar only
* PackTestZip64Manual.java still tests on the big jar

bug: https://bugs.openjdk.java.net/browse/JDK-8079769
webrev: http://cr.openjdk.java.net/~amlu/8079769/webrev.00/

Thanks,
Amy