Remove workspace fudge with proper fix to rbac

This IMHO a much better fix than the one I provided in PR: #1680. The fix seems obvious with hindsight. The RBAC code should not have been sending a possibly null/undefined method to the invokeRights method. Tested against recent snapshot (last weekend) of fabric8.
    
    The RBAC code should not have be calling invokeRights
    with an undefined method. Remove compensating code from
    workspace file and fix the rbac code.