find-delta: pass the cache-delta usage policy alongside the cache-delta...
find-delta: pass the cache-delta usage policy alongside the cache-delta
The idea is to give higher level code more control to what will happens with
the cache delta passed. This should help with controling how we treat delta's
from different sources.
The final goal of this change is to allow for server modes where the client can
blindly accept any server delta without regards to any local constraints. This
will be implemented in later changesets.
