RFR (XS): 8068540 - [TESTBUG] Exclude failing nightly tests

[George Triantafillou]

Please review this small fix for JDK-8068540.  The tests were modified 
with the "@ignore" jtreg tag to exclude them from nightly testing.

JBS: https://bugs.openjdk.java.net/browse/JDK-8068540
webrev: http://cr.openjdk.java.net/~gtriantafill/8068540/webrev.00/ 
<http://cr.openjdk.java.net/%7Egtriantafill/8068540/webrev.00/>

The fix was tested locally on Linux with jtreg and the JPRT hotspot testset.

-George