Deploy latest with its version tag

Kubernetes doesn't pull the `latest` tag automatically, so we need to change the
image tag in the deployment file.

As a plus, we can now see exactly what version we're running.

k8s/senpy-deployment.yaml

@@ -13,7 +13,7 @@ spec:
     spec:
       containers:
       - name: senpy-latest
-        image: gsiupm/senpy:latest
+        image: $IMAGEWTAG
         imagePullPolicy: Always
         args:
           - "--default-plugins"