RFR (XXS): 8132709: [TESTBUG] gc/g1/TestHumongousShrinkHeap.java might fail on embedded

[Dmitry Fazunenko]

Hello,

May I have reviews for a small test fix:
https://bugs.openjdk.java.net/browse/JDK-8132709

webrev:
http://cr.openjdk.java.net/~dfazunen/8132709/webrev/

Comments: the test allocates/deallocates a number of humongous objects 
to fragment the heap,
and then checks that fragmentation doesn't prevent heap shrinking. The 
test didn't expect that
the amount of free memory could be not enough to allocate several 
humongous objects (embedded platforms).
The fix adds such check.

Thanks,
Dima