Enable kubernetes SCTPSupport feature

The feature gate for sctp support in apiserver was added in
kubernetes 1.12 but is disabled by default.  This commit enables it.

Information about SCTP is here:
https://kubernetes.io/docs/concepts/services-networking/service/#sctp

The centos version of netcat can be used to validate the feature.
A Dockerfile for building a centos netcat is provided.

Tested by:

kubectl run --generator=run-pod/v1 --image netcat:v1.0.0 \
    listen-sctp -it --rm -- --sctp -l -p 9000

(get IP of the listener pod)
kubectl run --generator=run-pod/v1 --image netcat:v1.0.0 \
   test-sctp -it --rm -- --sctp <listener pod IP> 9000

Change-Id: I9642e485cb9c30f6b1272c00ec1046b9c98211ac
Story: 2006472
Task: 36403
Signed-off-by: Al Bailey <Al.Bailey@windriver.com>

puppet-manifests/src/modules/platform/templates/kubeadm.yaml.erb

@@ -17,6 +17,7 @@ apiServer:
     oidc-client-id: <%= @apiserver_oidc_client_id %>
     oidc-issuer-url: <%= @apiserver_oidc_issuer_url %>
     oidc-username-claim: <%= @apiserver_oidc_username_claim %>
+    feature-gates: "SCTPSupport=true"
 controllerManager:
   extraArgs:
     node-monitor-period: "2s"

tools/docker/images/Dockerfile

@@ -0,0 +1,4 @@
+FROM centos
+RUN yum install -y nc
+ENTRYPOINT ["nc"]
+CMD ["nc"]

tools/docker/images/Readme.rst

@@ -0,0 +1,5 @@
+export VERSION=v1.0.0
+sudo docker build \
+  --network host \
+  -t netcat:${VERSION} \
+  .