Ensure dshadmin home directory exists

[JimMadge]

Ensures appropriate ownership and permissions

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⤴️ Summary

The dshadmin home directory isn't created until the user logs in. If we use the serial console the directory is created with ownership root:root and so dshadmin is unable to write files. This is possibly because it bypasses pam_mkhomedir. In any case, it felt easier to make the directory and it's permissions part of the regular desired state.

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🔬 Tests

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