PDI-11985 - Error while trying to select .kjb in job executor step with Browse button, if connected to repository.

When using JobExecutorDialog or TransExecutor to select item on a
filesystem we used to get NPE.
This was caused by  attempt to set this
filename string back on UI after file successfuly picked.
For this cases we should use filename discovered from FS instead of using getFilename() method from job
meta.
Job meta will get this file name after executor's dialog will be closed.
No junits due to fix simplicity compare to difficults to write junits for
UI dialogs with private elements.
Merge pull request #554 from  prakapenka/PDI-11985