RFR: 8154500 fix handling of jdk.launcher.patch.* in tests

[Jonathan Gibbons]

The conversion from using sun.boot.class.path to jdk.launcher.patch.* 
was imperfect, and becoming more so with the move towards using multiple 
-Xpatch options, in different system properties.

A more complete/general solution would be shared infrastructure to fork 
tools and inherit selected jdk.launcher properties, but for now, I've 
done "quick and easy".

Bug: https://bugs.openjdk.java.net/browse/JDK-8154500
Review: http://cr.openjdk.java.net/~jjg/8154500/webrev.00/index.html

-- Jon