Arguments for Restic Check

[alexanderl19]

There are env variables (RESTIC_FORGET_ARGS, RESTIC_INIT_ARGS, RESTIC_JOB_ARGS) to pass arguments into their corresponding commands. An option to pass args into the restic check command would be useful for limiting download speed.

I don't believe that RESTIC_JOB_ARGS is passed to the check command. I'm happy to attempt a PR to either pass the args from RESTIC_JOB_ARGS into check or create a new RESTIC_CHECK_ARGS.