RFR: 8027960: Assertion assert(end >= start) failed during nightly testing on solaris

[Stefan Johansson]

Hi,

Please review this small fix for:
https://bugs.openjdk.java.net/browse/JDK-8027960

Webrev:
http://cr.openjdk.java.net/~sjohanss/8027960/webrev.00/

Summary:
The generation sizer needed to have its space-alignment updated when 
large pages are enabled. Right now only the gen-alignment was updated 
and then the spaces can grow to large to fit in the generation.

Testing:
JPRT standard testing
JTRG on JPRT

Thanks,
StefanJ