Use etcd v2 api prefix in etcd init.d script

Starting 3.4, default API for etcdctl commands is v3.
But v2 is still supported and extensively used in 3.4.
(source: etcd-io/etcd#12913)

Although it is a better idea to use v3 at as much places in
the code as possible, in case of cluster health API, v2 API gives
more clearer error about bad certificate usage than v3.
So it is better to stick to v2 than v3 at least in this case.

An environment variable ETCDCTL_API is used to specify
the usage of non-default version. A prefix for v2 API usage is added
to the only occurence of 'etcdctl' in the /etc/init.d/etcd script.

Test Plan:
PASS: Run '/etc/init.d/etcd status' with correct pair of certs.
      Etcd status is 'Running'.
PASS: Run '/etc/init.d/etcd status' with incorrect pair of certs.
      Etcd status is 'Running'.

Story: 2010878
Task: 48960

Change-Id: Idaaecfeec2c4851b4e33c21839df12cea5a65c2e
Signed-off-by: Kaustubh Dhokte <[email protected]>

puppet-manifests/src/modules/platform/files/etcd

@@ -44,9 +44,9 @@ ETCD_LISTEN_CLIENT_URL="${URLS[-1]}"
 status()
 {
     if [[ $ETCD_LISTEN_CLIENT_URL =~ "https" ]]; then
-        etcd_health="$(etcdctl --timeout 5s --ca-file /etc/etcd/ca.crt -cert-file /etc/etcd/etcd-server.crt --key-file /etc/etcd/etcd-server.key --endpoints="$ETCD_LISTEN_CLIENT_URL" cluster-health 2>&1)"
+        etcd_health="$(ETCDCTL_API=2 etcdctl --timeout 5s --ca-file /etc/etcd/ca.crt -cert-file /etc/etcd/etcd-server.crt --key-file /etc/etcd/etcd-server.key --endpoints="$ETCD_LISTEN_CLIENT_URL" cluster-health 2>&1)"
     else
-        etcd_health="$(etcdctl --timeout 5s --endpoints="$ETCD_LISTEN_CLIENT_URL" cluster-health 2>&1 | head -n 1)"
+        etcd_health="$(ETCDCTL_API=2 etcdctl --timeout 5s --endpoints="$ETCD_LISTEN_CLIENT_URL" cluster-health 2>&1 | head -n 1)"
     fi
 
     # LP: 2033942. In case if the status method is called in between