[BUG] core dump when using endpoint litellm

## Describe the bug
When executing litellm endpoint tasks in a directory on the distributed file system, such as glusterfs, it causes a core dump.

Maybe the root cause is that in “lighteval/models/litellm_model.py“, the litellm cache type used is "disk" without specifying a directory. In disk cache mode, litellm uses ./.litellm_cache as the default directory. When this directory is located on the glusterfs distributed file system, there may be conflicts with SQLite, which is the underlying storage engine of diskcache.

## To Reproduce
lighteval endpoint litellm ...

## Expected behavior

## Version info
commit b9a2e56