Don't return ServiceInstance in resolveClusterReferences and related methods (#2400)
Don't return ServiceInstance in resolveClusterReferences and related methods (#2400)

None of the methods is replacing the ServiceInstance, so there's no need
to return it (the returned value is always the same as the value passed
into the method).
jboyd01/service-catalog,jboyd01/service-catalog,jboyd01/service-catalog,jboyd01/service-catalog,jboyd01/service-catalog,jboyd01/service-catalog