RFR: 8057918: Update out-dated ignore tags in GC jtreg tests

[Stefan Karlsson]

Hi all,

Please review this patch to remove/fix a few jtreg @ignore tags.

http://cr.openjdk.java.net/~stefank/8057918/webrev.00/

The following bugs were fixed/changed:

Fixed:
https://bugs.openjdk.java.net/browse/JDK-8027915

Env problem:
https://bugs.openjdk.java.net/browse/JDK-8025645

Closed/duplicate:
https://bugs.openjdk.java.net/browse/JDK-8042051

thanks,
StefanK