Add cluster migration test in cache mode

This last comment makes me think that we are missing cluster migration test for dragonfly running in cache mode and for testing expire logic. Lets open a separate task for that and do this in a separate PR

_Originally posted by @adiholden in https://github.com/dragonflydb/dragonfly/pull/4197#discussion_r1895339014_

Start by reading the discussion in PR #4197, especially the referenced comment, and locate the existing cluster migration test coverage. Define a separate test for Dragonfly in cache mode that exercises expiration logic, then submit it in a separate PR.

Written by the indexing model from the issue text.