To fix instability and availability issues:
etcd3 is not available in repos for binary kolla images.
etcd3 does not support eventlet-based services [1].
[1] https://review.opendev.org/466098
Change-Id: I430bab735da204fc81696130b17931a89214c876
Closes-bug: #1852086
Closes-bug: #1854932
(cherry picked from commit 58b5acbf65)