Review request for 8028647: Add instrumentation in GetSafepointSyncTime.java and remove it from ProblemList.txt

[Mandy Chung]

Webrev at:
http://cr.openjdk.java.net/~mchung/jdk8/webrevs/8028647/webrev.00/

This patch turns the trace on by default and also add the 
instrumentation to print the safepoint count to help troubleshooting the 
test failure.

test/sun/management/HotspotRuntimeMBean/GetSafepointSyncTime.java is no 
longer reproducible on jdk8 b109.   GetSafepointSyncTime.java should be 
removed from the ProblemList.txt.    This still fails with 7u45 and so I 
want to backport this change to 7u-dev.   There might be a hotspot fix 
in jdk8 that resolves the zero safepoint sync time issue for further 
investigation.

thanks
Mandy