Use metadata instead of **metadata for claim's updates

In order to keep consistency with other methods (queue's upsert), this
patch replaces **metadata with metadata and implements some logic in
claim's create method.

Implements blueprint storage-base

Change-Id: Ibec9e8d07a2db4c1339f6fb7ba24de8820e0235d
Merge "Use metadata instead of **metadata for claim's updates"