SFC-Boron: Incorrect yang model for logical sff (SFF State)

The operational data model for SFF state (as defined in sfc-model/src/main/yang/service-function-forwarder-logical.yang) is incorrect:
1) It does not allow to store the list of DPN ids that are part of the logical SFF at a given time (this was precisely the purpose of this model fragment)
2) Does not allow to store the list of RSPs using a given dataplane node
3) The dictionary is unnecessary (it contains exactly the same information that is stored in the rendered service path state)

In addition to that, Boron version did not provide an implementation for this operational data model.

Note: API changes for correcting this bug are OK (this model fragment was introduced by us few months ago to support logical SFF functionality that we're implementing; there are no other clients / users / implementations for this model fragment)