WIP: atlas-probe & atlas-sw-probe: update

This PR updates atlas-probe with busybox packages and bumps the firmware version to 5020-2. It also tries to run processes as atlas user.

Note: since version 5020-2 5020-3 is now only in the devel branch in upstream, I'm not sure if we should merge this MR now. Anyway I run tested it and it worked ok ... as far as I know.