[nrf fromlist] Bluetooth: Host: Cancel pending deferred work on disconnect

This fixes an issue that occurred if deferred_work is queued by another
procedure before we run bt_conn_set_state(BT_CONN_DISCONNECTED).
bt_conn_set_state yields to the system work queue in bt_conn_tx_notify,
and then deferred_work runs and handles the disconnected callbacks.
bt_conn_set_state then enqueues another deferred_work which calls the
disconnected callbacks again and causes an assert. k_work_cancel_delayable
will clear queued deferred work when we call
bt_conn_set_state(BT_CONN_DISCONNECTED), guaranteeing that the disconnect
callbacks will only be called once.

Upstream PR #: 82543

Signed-off-by: Timothy Keys <[email protected]>
(cherry picked from commit 833b6d2)

Author: weeTike

subsys/bluetooth/host/conn.c

@@ -1264,6 +1264,11 @@ void bt_conn_set_state(struct bt_conn *conn, bt_conn_state_t state)
 		 */
 		switch (old_state) {
 		case BT_CONN_DISCONNECT_COMPLETE:
+			/* Any previously scheduled deferred work now becomes invalid
+			 * so cancel it here, before we yield to tx thread.
+			 */
+			k_work_cancel_delayable(&conn->deferred_work);
+
 			bt_conn_tx_notify(conn, true);
 
 			bt_conn_reset_rx_state(conn);