s3: Fix IsNotExist()
s3: Fix IsNotExist()

jayme-github/restic,kurin/restic,middelink/restic,middelink/restic,fawick/restic,restic/restic,ar-jan/restic,kurin/restic,fawick/restic,ar-jan/restic,restic/restic,jayme-github/restic