Blender Git Loki

Fix loss of cloth disk cache on reload in library overrides.

If the override system creates an override record for the cache
name (no idea why though), it trashes the disk cache on file load.

The reason is that it tries to rename cache files in update handler
when assigning the name, and BLI_rename deletes the target file even
if both names are the same.

This is a safe fix that simply aborts the pointless rename attempt.

Differential Revision: https://developer.blender.org/D13679