Comment 7 for bug 1913348

Also reported in https://bugs.launchpad.net/charm-etcd/+bug/1947034, in which Andrew shares a workaround (thanks!):

> As a quick fix, changing all entries of the ipv6 addresses in /var/snap/etcd/common/etcd.conf.yml to the correct ipv4 address for etcd up and running with a healthy peer.