corosync_ring_id_store: Use safer permissions

corosync_ring_id_store should use same (safer) permissions as
corosync_ring_id_create_or_load for (eventually) newly created ringid
file.

Credit to Sjerek for finding this problem.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>