Bugfix: Restic dump now interprets --host and --path correctly

Restic dump previously confused its --host=<host> and --path=<path>
options: it looked for snapshots with paths called <host> from hosts
called <path>. It now treats the options as intended.

https://github.com/restic/restic/issues/4211
https://github.com/restic/restic/pull/4212