importd: drop dkr support The current code is not compatible with current dkr protocols anyway, and dkr has a different focus ("microservices") than nspawn anyway ("whole machine containers"), hence drop support for it, we cannot reasonably keep this up to date, and it creates the impression we'd actually care for the microservices usecase.

importd: fix bus policy

import: introduce new mini-daemon systemd-importd, and make machinectl a client to it The old "systemd-import" binary is now an internal tool. We still use it as asynchronous backend for systemd-importd. Since the import tool might require some IO and CPU resources (due to qcow2 explosion, and decompression), and because we might want to run it with more minimal priviliges we still keep it around as the worker binary to execute as child process of importd. machinectl now has verbs for pulling down images, cancelling them and listing them.