[openFATE 308758] bs_worker should support rpm caching also for product builds

Feature changed by: Adrian Schröter (adrianSuSE) Feature #308758, revision 6 Title: bs_worker should support rpm caching also for product builds - Buildservice: Candidate + Buildservice: Done Priority Requester: Important Projectmanager: Mandatory Requested by: Adrian Schröter (adriansuse) Developer: (Novell) Description: A remote bs_worker (means not on main server), which builds products is not able to cache the rpm binaries atm. This makes it in-efficient to build products and we can't build up dedicated image build hosts atm. Caching for this mode should be implemented. -- openSUSE Feature: https://features.opensuse.org/308758