8241415: tools/jpackage/share/RuntimePackageTest.java fails because of systemPrefs files

[Baesken, Matthias]

Hi Alan,

>Tests should never modify the "JDK under test". 

That was my assumption too.

>It should be possible to 
>test a JDK that is on a read-only file system for example. There are a 
>small number of tests that need  edit configuration files and they are 
>supposed to replicate the JDK to another location so it doesn't 
>interfere with other tests running at the same time or later. For the 
>prefs API, there are system properties (java.util.prefs.systemRoot and 
>java.util.prefs.userRoot) to configure where the system and user prefs 
>are stored. There were several issues in the past with userRoot and I 
>think all those tests were fixed to run the tests with the system 
>property set. We might have to do a similar exercise for the systemRoot.

Hopefully we can identify the "bad guys" in the test set without too much effort �� !

Best regards, Matthias