totem: fix check if all nodes have name attrs in multi-link setups

As totem_config->interfaces entries are _all_ possible links and not
only the configured ones we cannot trust that interface[0] is
configured at the time of checking, and thus has a valid
member_count. So set the members variable to the member_count entry
from an actually configured interface and loop over that one.

This fixes a case where the check for the name property on all nodes
for multi links was skipped if link 0 was not configured, as then its
member_count was 0.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>