Generate thumbnail for LOCAL Remote Storages

As it is now, Kaltura can only generate thumbnails for entries which are in the main DC, i.e. using the default storage space that comes with kaltura (/web/content/entry/data...).
In order to generate thumbnails for entries which are stored in a remote storage, there has to be a flavor that remains in that main DC.
Nevertheless, if you are using a Remote Storage configured as LOCAL, you can access locally to it, so I've made this modification which checks if this is the case, and then builds the source path for the video to generate correctly the thumbnail.