RFR: 8168396: Unexpected OOME in GcCauseTest02 and GcTest02

[Michail Chernov]

Hi,

Could you please review this change?

http://cr.openjdk.java.net/~mchernov/8168396/webrev.00/
https://bugs.openjdk.java.net/browse/JDK-8168396

Initial heap size and max heap size were made equal to guarantee 
expected memory allocation. Previous version of test can throw OOME 
because does not consider existing free heap size.

Thanks,
Michail