This callback function is called in response to a flow query request
submitted to the flow cache service. The module handling this callback
can be different from the one that submitted the query. In the flow
query object used for submitting the flow query, the identity of the
callback handler is passed. When flow cache service has all or some
of the flows that needs to be returned then this callback is called
for the appropriate module. The respone contains a boolean more flag
that indicates if there are additional flows that may be returned
via additional callback calls.
resp - the response object containing the original flow query
object, partial or complete list of flows that we queried and some
metadata such as the more flag described aboce.