Cellular Network Infrastructure » osmo-ePDG - VoWifi Evolved Packet Data Gateway

When the IKEv2 SA got destroy we should
- inform osmo-epdg via GSUP (Msg: Purge MS Request)
- remove internal state

Use listener api ike_updown() + ike_rekey() to get notified about changes in the SA.
The python SWu-IKEv2 doesn't seem good enough to test this. Only ike_rekey() can be tested.

Reducing the timeout of the ike SA might help to provoke the code path.