Fix test for accompanying text upload.

Fixes ISLANDORA-855
Fix error handling around exec()

The way the exec() call was being handled meant the $success variable
was not being set correctly  Fixed by explicitly checking the
return code parameter of exec().  Also used the watchdog facility
to log detailed error information from exec().
Merge pull request #36 from lyrasis/lyr-master

Fix test for accompanying text upload and incorrect error handling around exec()