jpackage tests on Windows leave large temp files

Some of the jpackage tests write to temp instead of the jtreg scratch file, these files aren't cleaned up after test execution and quickly fill up the disk.

Each test seems to leave around 170MB in temp:

dir /s cygwin\tmp\jdk.jpackage13029007297622725429

...

     Total Files Listed:
             285 File(s) 176,786,554 bytes