Install etcd binary from github

Removes a dependency on RDO for install etcd in CentOS images.

Aligns version of etcd across all distributions, see below:

```
(venv-kolla) [will@juno kolla]$ docker run --rm -it kolla/ubuntu-source-etcd:yoga bash
()[etcd@730a011b670a /]$ etcd --version
etcd Version: 3.2.26
Git SHA: Not provided (use ./build instead of go build)
Go Version: go1.13.7
Go OS/Arch: linux/amd64
```

```
(venv-kolla) [will@juno kolla]$ sudo docker run -it kolla/centos-source-etcd:yoga bash
()[etcd@9aa486c9e94f /]$ etcd --version
etcd Version: 3.2.21
Git SHA: 3ac81f3
Go Version: go1.12.8
Go OS/Arch: linux/amd64
```

```
(venv-kolla) [will@juno kolla]$ docker run --rm -it kolla/debian-source-etcd:yoga bash
()[etcd@b49cb5fcdf87 /]$ etcd --version
etcd Version: 3.3.25
Git SHA: Not provided (use ./build instead of go build)
Go Version: go1.15.9
Go OS/Arch: linux/amd64
```

This will also allow us to update to a more recent version in the
future. We have to be careful not to jump by more than one point release
to ensure compatibility:

https://etcd.io/docs/v3.5/upgrades/upgrading-etcd/#upgrading-an-etcd-v3x-cluster

Change-Id: I62a34256fb7395d0448af169ac3cf036f60cd290

1 files changed, 6 insertions, 0 deletions

diff --git a/releasenotes/notes/etcd-binary-install-fc88930f4bf6ce2c.yaml b/releasenotes/notes/etcd-binary-install-fc88930f4bf6ce2c.yaml
new file mode 100644
index 000000000..d76ee06a1
--- /dev/null
+++ b/releasenotes/notes/etcd-binary-install-fc88930f4bf6ce2c.yaml
@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    ``etcd`` is now installed from the upstream binaries published to github
+    rather than via the OS package manager. This aligns the etcd version across
+    all distributions for compatibility.