RFR: 8157090: SharedArchiveFile/SpaceUtilizationCheck.java fails as space utilization is below 30 percent

[Claes Redestad]

Hi,

JDK-8150044 sought to decrease the shared archive read only size to 8M 
to appease this test, but the setting was increased back to 9M due to a 
problematic merge.

I think we can more aggressively lower the min and default sizes on 
32-bit. 6M brings RO to 59.7% used, RW to 44.2%, and passes all related 
tests:

Webrev: http://cr.openjdk.java.net/~redestad/8157090/webrev.01/
Bug: https://bugs.openjdk.java.net/browse/JDK-8157090

Testing: JPRT -testset hotspot,

/Claes