Review request: 7127448 Regression test scripts for policytool need to recognize macosx

[Jason Uh]

http://cr.openjdk.java.net/~juh/7127448/webrev.00/ 
<http://cr.openjdk.java.net/%7Ejuh/7127448/webrev.00/>

Could I get the above change reviewed please? A simple addition for 
tests to recognize Darwin.

Thanks,
Jason