fix: Ensure kubeconfig ends with \n (#880)

In order to be a text file according to POSIX, file needs to be composed of
text lines. Text line is defined as sequence of characters ending in \n. Sadly,
`~}` did strip everything including the \n, so the kubeconfing did not end
with a new line. Output empty string at the end to make sure of it.

templates/kubeconfig.tpl

@@ -35,4 +35,4 @@ users:
         - name: ${k}
           value: ${v}
   %{~ endfor ~}
-%{ endif ~}
+%{ endif }