We cannot rely on the implicit IPA keepalive FSM termination, as that
somehow gets the termination order wrong and we end up accessing free'd
memory.
Let's handle the termination explicitly: We register a callback with
the IPA keepalive FSM, and once that callback gets hit, we ask the
core to *not* terminate the FSM implicitly. We are anyway terminating
it explicitly in st_reestablish_onenter().
Change-Id: Ia745ccb44c0d0224d1e7ab6b6da3713474111d41