Fixed EZP-20687: Existing file path outside the current vardir throws an exception

*WORK IN PROGRESS*

Only Image is affected, since BinaryFile and Media both store the filename, and rebuild the path dynamically.

The fix catches the IO exception in ImageStorage, and logs an error.

Spec tasks:
- [ ] Consider handling this purely at Legacy level, with BC only logging. Try reading the file, possibly security checks on the string. Shall we prevent writing completely ?

Tech tasks:
- [x] Catch the IOService exception, and log an error in ImageStorage
- [ ] Consider using a dedicated exception in order to make this Legacy only
- [ ] Enhance the test
- [ ] Try to make the image "usable" in read mode
- [ ] See what was supported in Legacy when an image had such a path, and update accordingly