Followup EZP-22917: make eZFSFileHandler::fileDelete() less verbose
After e9bfd8cea8, eZDir::recursiveDelete() has been made verbose, and
clearing all caches results in such error message:

[ Jul 04 2014 16:33:47 ] [] eZDir::recursiveDelete:
The path: var/cache/ini is not a folder

Mimic what is done in eZFSFileHandler::delete() by checking if the path
given to eZDir::recursiveDelete() is a directory.