agent: publish unit state regardless of hash

When starting up, the Agent may already have some Jobs loaded. In this
case, the UnitStatePublisher will not have a cached hash for the
corresponding Unit. The UnitStatePublisher must publish state regardless
of the UnitHash being absent.
agent: overlay loaded states on local units

When starting up, the Agent may already have some Jobs loaded. These
Jobs must be introduced to the Reconciler with an inactive state in
order to properly build the cache.