* etcd 3.3 is no longer maintained.
* etcd 3.4 removes deprecated interfaces, and clients may
need updated configs.
* The cinder backend coordination URL needs to explicitly
specify the version, until tooz can be updated
https://review.opendev.org/c/openstack/tooz/+/891355
* etcd only supports in-place upgrades between minor
versions, so any jobs testing upgrades could fail if
they skip from 3.2 directly to 3.4
Change-Id: Ifcecdffa17a3a2b1075aa503978c44545c4a2a3c
3a7a3cd8c5