some smb servers are very insistent in reporting that the root of the share is readonly, even if it isn't.
This works around the problem by adding a hidden option to overwrite the permissions of the root of the share.
This can be enabled using
```bash
occ files_external:config <mount id> root_force_writable true
```
where you can find your mount id using
```bash
occ files_external:list
```
Signed-off-by: Robin Appelman <robin@icewind.nl>
ec0ca19deb