kitchen: Pin to amd64 nodes

There is not (currently) an aarch64 build of the kitchen screen server,
so we need to force the pod to run on a x86_64 node.  This seems a good
candidate for running on a Raspberry Pi, so I should go ahead and build
a multi-arch image.

kitchen/kitchen.yaml

@@ -49,6 +49,8 @@ spec:
           mountPath: /kitchen.yaml
           subPath: config.yaml
           readOnly: true
+      nodeSelector:
+        kubernetes.io/arch: amd64
       securityContext:
         runAsNonRoot: true
         runAsUser: 17402