Podman: Mounting volumes with `z` to work around permission issues

[olemartinorg]

Description

Related Issue(s)

• {issue number}

Verification

• [ ] Your code builds clean without any errors or warnings
• [ ] Manual testing done (required)
• [ ] Relevant automated test added (if you find this hard, leave it and we'll help out)
• [ ] All tests run green

Documentation

• [ ] User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[olemartinorg]

I haven't spent time yet trying to reproduce the problems to make sure this fix works all the time, but I guess this could be one step on the road to something stable, at least.