The old attachment API has a mix of OVO and DB method calls that can
result in admin metadata being removed.
When we automatically update the admin metadata using DB methods these
changes are not reflected in the volume OVO, so when we pass the OVO via
RPC the receptor will assume that admin metadata present in the OVO is
up to date, and will delete key-value pairs that exist in the DB and are
not in memory.
That is happening on the old `attach` method with the `readonly` key
that gets removed by the volume service after it was added (calling the
DB) on the API service.
Patch doesn't include a release note to avoid making unnecessary noise
in our release notes, because it is unlikely to affect existing users
since Nova will be using the new attachment API.
Change-Id: Id3c7783a80614e8a980d942343ecb9f47a5a805a
779b0249fa