Adds initial database 'migration' tests

As we only have v1 of models/api right now, not possible to do 'proper'
migration tests. This just adds checks that the database tables are
created 'correctly' (as defined by v1 migration definitions) @
tuskar/db/sqlalchemy/migrate_repo/versions/001_init.py.
Also calls the db_sync to make sure there are no errors there. Uses
sqlite in memory.

Change-Id: Ib56fc20c0a93839e1913c3a0d04ad772abb6f688