Add flavor-from-sysmeta-to-blob spec

Flavor data is currently stored inefficiently in system_metadata and
should be moved to being stored as a blob in an appropriate place
per-instance. This will facilitate storing additional flavor details
that we badly need, such as extra_specs.

Change-Id: I4a06d6c0ff3b9db0b3bde17e78afad1a4de1457a
Merge "Add flavor-from-sysmeta-to-blob spec"