cluster init: Write ssconf before noded starts

This change is needed as we will need to read the primary ip version
cluster parameter before we start the node daemon. The reason is that we
need to know in advance if we bind to the IPv4 or IPv6 any address.

Signed-off-by: Manuel Franceschini <livewire@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>