Users need to set:
"packRelated": true,
... in their server config. This will probably become the default
value in the future.
This is currently mutually exclusive with diskpacked, which isn't good
at deleting things, and blobpacked loves to delete things (from the
loose blobs).
Updates #532
Change-Id: I8f4ea9406859b2705f26e9d1103d3acf9d1a8411
Brad Fitzpatrick