quota_include_external_storage is ignored while uploading using the NextCloud client

[r3pek]

Steps to reproduce

1. Set quota_include_external_storage = false
2. set a user's quota = 0
3. create a file on an external storage via web browser
4. create a file on the "local external folder" synced by the nextcloud desktop client

Expected behaviour

Steps 3 and 4 should both work.

Actual behaviour

Step 4 fails with "insufficient storage available"

[MorrisJobke]

cc @icewind1991

[MorrisJobke]

Could be related to #4816

[MorrisJobke]

Fixed by #6483