s4-repl: Allow dsdb_replicated_objects_commit() to use different schema while committ...

s4-repl: Allow dsdb_replicated_objects_commit() to use different schema while committing objects

working_schema is to be used while committing a Schema replica.

When we replicate Schema, then we most probably won't be
able to convert all replicated objects using the current
Schema cache (as we don't know anything about those new objects).

Thus, during Schema replication, we make a temporary
working_schema that contains both our current Schema +
all objects we get on the wire.
When we commit those new objects, we should use our working_schema
(by setting it to the ldb), and after all changes are commited,
we can refresh the schema cache so we have a brand new,
full-featured Schema cache