This allows specifying functions that further optimize the scheduling
of shares across backend stanzas.
This is needed due to a netapp-driver specific problem when using
SVM scoped accounts. It does not have enough permissions to obtain
the total_capacity_gb information, so it cannot calculate utilization,
and therefore the goodness_function always returns 50 and end up
scheduling shares always to the same pool.
Closes-bug: #2073537
Change-Id: Ia151c50421e75282f633e0b004c2e6c1bda638f3
94a4d30901