RFR (XXS): 8098834 - Update jprt.properties with property listing tests subtrees

[Dmitrij Pochepko]

Hi,

Please review this small fix.
A new property for jprt, listing directories used for regression tests

bug: https://bugs.openjdk.java.net/browse/JDK-8098834
webrev: http://cr.openjdk.java.net/~dpochepk/8098834/webrev.01/

Thanks,
Dmitrij