metabase has become a central concept and it's more suitable for it to
be directly nested under satellite rather than being part of metainfo.
metainfo is going to be the "endpoint" logic for handling requests.
Change-Id: I53770d6761ac1e9a1283b5aa68f471b21e784198
metabaseSegmentKey` TransferQueueItem
We are unifying which name (and type) we are using for value we are
using to point to segment. We want to use `key` instead of `path`.
Dedicated type `metabase.SegmentKey` was created for this purposes also.
This change is doing refactoring around gracefulexit.
Change-Id: I90d51ff087b206179e61d5f1bc95f4709d76f917
