core.loader: Allow core loader to update origin_visit in one call
Prior to this commit, subclasses were in charge of setting the snapshot (for an origin_visit).
There ended up being 2 origin_visit_update
calls, 1 in the subclass to set
the snapshot id, then 1 in the loader core to set the visit (e.g. svn loader)
Motivation:
Make the origin_visit_update
status parameter mandatory.
Preparatory work for T2310
Test Plan
tox
Migrated from D2887 (view on Phabricator)