RFR (XS): JDK-8027450 : Improve time reporting in G1 remark

[Joseph Provino]

Hi all,

Can I have reviews for the following small change that logs more G1 
Concurrent Mark
Trace Times.  I also changed G1RemarkGCTraceTime() to G1CMTraceTime() 
because it's
used in places other than remark.

CR: https://bugs.openjdk.java.net/browse/JDK-8027450

Webrev:http://cr.openjdk.java.net/~jprovino/8027450/webrev.00/

Testing: jprt

I also need a sponsor to commit the changes.
Thanks.

joe