[Rigo] use direct access to the installed packages repository, avoid locking

Locking is too expensive, and using memory cached data may result
in huge inconsistencies due to stale data. Direct mode allows to
skip memory cache and read data directly from the database storage.
However, entropy.db.sqlite queries using memory caches did not
perform very well when cache is cold. But this has been solved by
directed() already (a different query is run if memory cache is disabled).