When launching many containers gitea admin waiting still sometimes gets stuck.
This should provide a bandaid for now. Also improve the container detection.
Admin deployment was very timing-dependent: If the server took a while
to set it up, it would always error out while deploying. This commit
adds sufficient grace-time into the admin request call before the error
occurs which should avoid it in most deployments (unless the server is
severely underpowered or over-taxed).
Also fixes admin creation to avoid root usage in the container when it
is not called for.
