Description of problem:
If the export destination is in a different partition than `/var/lib/pulp/media` then syncable exports raises an eroor along the lines of
` Invalid cross-device link `/var/lib/pulp/media/artifact/7a/831f9f90bf4d21027572cb503d20b702de8e8785b02c0397445c2e481d81b3' -> '/exports/repo/Packages/b/bear-4.1-1.noarch.rpm'`

Version-Release number of selected component (if applicable):
Sat 6.11.2

How reproducible:
Always

Steps to Reproduce:
1. Administer -> Settings -> Content -> Set 'Pulp 3 export destination filepath' to a path that is in a different partition from /var/lib/pulp/exports
2. Add the partition path to `ALLOWED_EXPORT_PATHS` in `/etc/pulp/settings.py` and restart services
3. Make sure pulp user has write access to that path
4. Sync a custom repo in your satellite
5. `hammer content-export complete repository --id=<repo id> --format=syncable`

Actual results:
Error along

```
Error: [Errno 18] Invalid cross-device link:

/var/lib/pulp/media/artifact/7a/831f9f90bf4d21027572cb503d20b702de8e8785b02c0397445c2e481d81b3' -> '/exports/Default_Organization/cv/2.0/2022-09-09T02-42-15-00-00/custom/custom/repo/Packages/b/bear-4.1-1.noarch.rpm'
```
Expected results:

It should be writing to a new partition instead of trying to symlink.

Additional info: