Changes

Gb/NS: SNS: SNS Ack don't add List of IP4/6 Elements on success.

The List of IP4/6 Elements should be only present on a SNS Ack
if the procedure fails with cause code Unknown IP Endpoint.
However ns2 code appended the List always to the SNS Ack.

Remove List of IP4/6 Elements from SNS Add, it can't fail with Unknown IP Endpoint.
Remove List of IP4/6 Elements from SNS Change Weight success case.

Related: OS#6611
Change-Id: If99b204a9d754323e53746b31bc13df53a653b7d