Make sure root UID/GID are mapped properly

[ryanlovett]

I've discovered that UID 0 / GID 0 is being mapped to 65534 on a local system in a server spawned with portwrap. This was flagged when a user attempted to use git/ssh from this jupyter server, and ssh complained that a file in /etc/ssh/ssh_config.d/ had the wrong permissions. They are 65534:65534 within the user namespace and 0:0 on the host. I suspect this is happening because of how subuid/subgid are configured on the system, but I need to test.

[ryanlovett]

Actually, it looks like this is due to how bubblewrap initializes the namespace, to not map root-to-root. There may be other code paths to take if bubblewrap were setuid, but I'm not sure what all the pros and cons to that are.