Add an auto-fix broken media step to the scanner job

[kkovaletp]

Is your feature request related to a problem? Please describe.
While most media viewers are able to auto-fix some small inconsistencies in the media files and show them correctly, our scanning job is sensitive to all of them, so if a media has some small inconsistency, the job marks it as broken and does not create a thumbnail. With the recent fix in master it doesn't lead to skipping all other media in the same folder, but still, this is not the best way to handle this case.

Describe the solution you'd like
It would be great to have some auto-fix media step as part of our scanner job (like ImageMagick for images and something similar for videos), so that even broken media can still be scanned and shown in the gallery.

Describe alternatives you've considered
An alternative is to manually run those fixing tools for all the media files, reported to be broken by the job.

[kkovaletp]

It would be easier to develop this feature after #929 is merged