RFR: JFR: oldobject/TestG1.java can't find leaking object

[Erik Gahlin]

Hi, 

Could I have review of a fix that repeats a test if it fails. One reason for failure is if the TLAB sampling is unlucky and doesn’t sample the object when a TLAB is used.

I did a similar update for Serial och Parallell.

We should probably add a test ZGC as well, but I will do that as an enhancement fix later.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8242501

Webrev:
http://cr.openjdk.java.net/~egahlin/8242501/

Testing: jdk/jdk/jfr/oldobject/*

Thanks
Erik