osmo-stp segfaults if IPA client connects to AS with routing-key != 0
When using something like this
as mahlzeit ipa routing-key 1005 5
and then connecting an IPA client, we crash in
ipa_asp_fsm_wait_id_ack2()which contains an
OSMO_ASSERT(as). The assert fails as we look-up the assert with a static routing-context of '0' (IPA doesn't allow us to transport a routing context in the message), which fails.
This is similar to #4233
The proper solution is probably to prevent the user from ever configuring a non-zero routing context for IPA AS.