RFR: 8073669: gc/TestSoftReferencesBehaviorOnOOME.java times out in nightlies

[Andrey Zakharov]

Hi, team.
I've
     changed test scenario to more straight-forward one,
     added tricks to prevent compiler optimizations and
     added checks when OOME didn't thrown as expected.

webrev:
     http://cr.openjdk.java.net/~azakharov/8073669/webrev/
testbug:
     https://bugs.openjdk.java.net/browse/JDK-8073669

testing: done in jprt, looks good now.

Thanks.