RFR: 8038947 HotSpotDiagnosticMXBean/CheckOrigin.java 'NewSize' should have origin 'ERGONOMIC' but had 'DEFAULT'

[Staffan Larsen]

This test verifies the origins of a couple of flags. One origin type is ERGONOMIC. The test used NewSize as an example flag that was set ergonomically by the JVM. It turns out that flag is not always set ergonomically. 

This change switches to use UseParNewGC as the ergonomic flag. This flag is set whenever UseConcMarkSweepGC is used.

webrev: http://cr.openjdk.java.net/~sla/8038947/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8038947

Thanks,
/Staffan