The recent change to process_add() to detect duplicate process
additions relies on the fact that all processes will be initialized
using process_init_stopped() before being passed to that function.
The autoassociation process was not initialized in this fashion, so
process_add() erroneously detected it as a duplicate.

Fix by using process_init_stopped() to initialize the autoassociation
process instead of setting the step member directly.

Signed-off-by: Michael Brown <mcb30@etherboot.org>