Fixed an issue where without a default GW, ansible_default_ipv4 would return an empty dict which passed as a valid fallback_ip dict item (#5394)

roles/kubespray-defaults/defaults/main.yaml

@@ -403,10 +403,13 @@ contiv_global_as: "65002"
 contiv_global_neighbor_as: "500"
 
 # Set 127.0.0.1 as fallback IP if we do not have host facts for host
+# ansible_default_ipv4 isn't what you think.
+# Thanks https://medium.com/opsops/ansible-default-ipv4-is-not-what-you-think-edb8ab154b10
 fallback_ips_base: |
   ---
   {% for item in groups['k8s-cluster'] + groups['etcd'] + groups['calico-rr']|default([])|unique %}
-  {{ item }}: "{{ hostvars[item].get('ansible_default_ipv4', {'address': '127.0.0.1'})['address'] }}"
+  {% set found = hostvars[item].get('ansible_default_ipv4') %}
+  {{ item }}: "{{ found.get('address', '127.0.0.1') }}"
   {% endfor %}
 fallback_ips: "{{ fallback_ips_base | from_yaml }}"