Since we recently increased a bit the timeout to assume the BSSAP_LE peer (SMLC) is implicitly up, the function f_bssap_le_wait_sccp_peer_available() may still be onging when we drop the sctp connection at the STP in the test, which will generate an explicit DUNA towards BSSAP_LE and hence fail the test because it never comes back available before it times out.
Since we don't need nor test SMLC in this test, simply disable starting the SMLC here to avoid this race condition and simplify the test.
hnbgw: Fix race conditions during PFCP Association
Since osmo-hnbgw now sends Heartbeat Requests, we need to take that into account. Furthermore, since it also now supports retriggering association when detecting peer restarted upon rx of Heartbeat Req, use that to trigger an association to clean up state and have a deterministic way to synchronize at that point regarding state.
