Revert "Remove hardcoded foreign keys from db.catalog.api"

It uses SqlAlchemy 0.8, which doesn't fit global requirement
sqlalchemy>=0.7.8.

This reverts commit f960c88209c78bc4075de70a10231552748dbff9.

Change-Id: I97ca02519856e2c183af6c8e0b7f4731b94490f9