getty restarts then dies for variants that already have a shell

**Image I'm using:**

metal-dev

**Issue or Feature Request:**

metal-dev boots and displays a login prompt. Then, the admin container starts and seems to try to take over tty0, which upsets getty and causes it to restart frequently, then die, making the local console unusable. :(

Start by reproducing the metal-dev boot sequence and observe how the admin container interacts with tty0 and getty after the login prompt appears. Trace the restart-and-die behavior; done means getty remains running and the local console stays usable after the admin container starts.

Written by the indexing model from the issue text.