fixed restic-check does not retry backend.Test failures
fixed restic-check does not retry backend.Test failures

added missing RetryBackend.Test implementation

Signed-off-by: Igor Fedorenko <78b6854e22ab09d4ae3dac29b92052963103b33e@ifedorenko.com>

kurin/restic,restic/restic,middelink/restic,restic/restic,kurin/restic,middelink/restic