fix: Do not set a guest name on actual users

[juliushaertl]

Should fix using the wrong user for filesystem access as described in nextcloud/server#40090

Before this the node was obtained from the share owner which caused issues getting the relative path later on

Debugger screenshot for my own reference:

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Documentation (manuals or wiki) has been updated or is not required

[SystemKeeper]

Works fine for me and solves nextcloud/server#40090 👍
Thanks!

[juliushaertl]

@elzody Do you remember what the intention of the change in 63aece8#diff-7a3746877ab19393cc83236c399a1a05d24b6dd96ddc1bfa2985b74108a04ca2R202 was?

[elzody]

@juliushaertl I can't recall, I think it was confusing logic for me and I accidentally had the wrong approach there. It makes sense now with this, and if it indeed fixes the issue, looks good from my side

[juliushaertl]

/backport to stable30

[juliushaertl]

/backport to stable29

[backportbot]

The backport to stable29 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable29
git pull origin stable29

# Create the new backport branch
git checkout -b backport/3948/stable29

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick ddc825dc

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3948/stable29

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[juliushaertl]

/backport to stable28

[backportbot]

The backport to stable28 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable28
git pull origin stable28

# Create the new backport branch
git checkout -b backport/3948/stable28

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick ddc825dc

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3948/stable28

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[juliushaertl]

/backport to stable27

[backportbot]

The backport to stable27 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable27
git pull origin stable27

# Create the new backport branch
git checkout -b backport/3948/stable27

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick ddc825dc

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/3948/stable27

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.