Changes

RAW_NS: SNS Changeweight: remove IPv4/IPv6 element in SNS Ack

When changweights of a NS-VC via SNS, the SNS Ack should
only contains the IEs "List of IP4/6 elements" if the cause code is
Unknown IP endpoint.

However the libosmocore/ns2 code isn't following this behavior yet.

Change-Id: Ibf00cbab0c6691cdb72fe592ee30e122dd8f4783