Startup environment issues when starting a cached image

[mafredri]

When starting a cached image, there is currently a few issues we need to iron out:

• We don't sanitize the environment (envbuilder options are present)
• Remote repo build option triggers a needless clone at startup
• We skip execution of some lifecycle scripts

This list may not be exhaustive and there may be additional edge cases which need to be handled.

Issues that are present even in the absence of cached image, but can be relevant for a smooth user experience:

• If repo is present, we don't fix permissions even if repo is owned by root:root and we're running as a user (this happened to one of my development workspaces)