networkd-link: Don't start a DHCPv6 informational exchange automatically

When a link is configured, wait until there is a Router Advertisement before
attempting to start DHCPv6. The intended DHCPv6 mode will be evaluated in
ndisc_router_handler() in networkd-ndisc.c.

src/network/networkd-link.c

@@ -1629,18 +1629,6 @@ static int link_acquire_ipv6_conf(Link *link) {
 
         assert(link);
 
-        if (link_dhcp6_enabled(link)) {
-                assert(link->dhcp6_client);
-                assert(in_addr_is_link_local(AF_INET6, (const union in_addr_union*)&link->ipv6ll_address) > 0);
-
-                /* start DHCPv6 client in stateless mode */
-                r = dhcp6_request_address(link, true);
-                if (r < 0 && r != -EBUSY)
-                        return log_link_warning_errno(link, r,  "Could not acquire DHCPv6 lease: %m");
-                else
-                        log_link_debug(link, "Acquiring DHCPv6 lease");
-        }
-
         if (link_ipv6_accept_ra_enabled(link)) {
                 assert(link->ndisc);