Add --dry-run option for garage-deploy.
Add --dry-run option for garage-deploy.

Fetches everything and checks for presence on push server but does NOT
actually push or sign anything.

advancedtelematic/sota_client_cpp,advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/sota_client_cpp,advancedtelematic/aktualizr