Revert back to using an empty var as default to exclude hostname (#2110)

roles/kubernetes/node/defaults/main.yml

@@ -80,7 +80,6 @@ kube_hyperkube_image_repo: ""
 # If non-empty, will use this string as identification instead of the actual hostname
 kube_override_hostname: >-
   {%- if cloud_provider is defined -%}
-  false
   {%- else -%}
   {{ ansible_hostname }}
   {%- endif -%}