RFR: 8232686: Turn parallel gc develop tracing flags into unified logging

[Ivan Walulya]

Hi all,

Please review a small modification to  turn parallel gc develop tracing flags into unified logging

Bug: https://bugs.openjdk.java.net/browse/JDK-8232686 <https://bugs.openjdk.java.net/browse/JDK-8232686>
Webrev: http://cr.openjdk.java.net/~sjohanss/iwalulya/8232686/00/ <http://cr.openjdk.java.net/~sjohanss/iwalulya/8232686/00/>

Testing: Tier 1 - Tier 3

//Ivan