Manifest invalid message in the Docker GC task

If run Docker GC task show message for some assets `manifest invalid`.

It happens because in the repository we have empty blob /blobs/sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4 which has kind METADATA but it should be BLOB. Fixing asset kind from METADATA to BLOB will remove the asset from the Docker GC filter which tries to find all METADATA assets.

Acceptance: 

• The Orient codebase contains a fix 
• new DB codebase also contains a fix 
• New Integration test covers the fix. 
• Migration is created to update the old incorrect blobs in the repository 
  • Migration for orient 
  • migration for new DB