ike-sa: Fix handling of redirects during IKE_AUTH

ike-sa: Fix handling of redirects during IKE_AUTH

Since the referenced commit, the state switch to IKE_ESTABLISHED doesn't
happen immediately after completing the authentication but only after
the remaining tasks have finished.  Due to that redirects during IKE_AUTH
were treated like those during IKE_SA_INIT causing the IKE_SA and task
manager to get reset.  However, unlike the ike-init task, the ike-auth
task returned SUCCESS and, therefore, got destroyed, while a different
task was removed from the array that was modified during the reset.
This later caused a dereference of the freed ike-auth task and a crash.

Fixes: 5ce1c91b58a2 ("ikev2: Trigger ike_updown() event after all IKE-specific tasks ran")