RFR: JDK-8229252 : Add descriptions to Windows jtreg tests

[Alexey Semenyuk]

Please review the jpackage fix for bug [1] at [2].

This is a fix for the JDK-8200758-branch branch of the open sandbox 
repository (jpackage).

- Add comments to Windows jtreg tests to help SQE setup their testing.

[1] https://bugs.openjdk.java.net/browse/JDK-8229252

[2] http://cr.openjdk.java.net/~asemenyuk/8229252/webrev.00/

Thanks,
Alexey