Bugfix: Correct `restore` progress information if an error occurs

If an error occurred while restoring a snapshot, this could cause the `restore`
progress bar to show incorrect information. In addition, if a data file could
not be loaded completely, then errors would also be reported for some already
restored files.

Error reporting of the `restore` command has now been made more accurate.

https://github.com/restic/restic/pull/4624
https://forum.restic.net/t/errors-restoring-with-restic-on-windows-server-s3/6943
