Clean up shuffle files once their metadata is gone

Previously, we would only clean the in-memory metadata for consolidated
shuffle files.

Additionally, fixes a bug where the Metadata Cleaner was ignoring type-
specific TTLs.
Merge pull request #279 from aarondav/shuffle-cleanup0

Clean up shuffle files once their metadata is gone

Previously, we would only clean the in-memory metadata for consolidated shuffle files.

Additionally, fixes a bug where the Metadata Cleaner was ignoring type-specific TTLs.