javaunohelper: migrate PropertySet_Test to JUnit

$ make JunitTest_juh

Change-Id: Ie6ed5070db01d8c183ddaae1852117667eae02f3
Reviewed-on: https://gerrit.libreoffice.org/11668
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>