fix typo in "kibana_base_url" variable name
fix typo in "kibana_base_url" variable name

This typo lead to kibana_base_url being undefined and Kibana used
default base URL ("/") which is incorrect with default proxy-based
access.

kubernetes-sigs/kubespray,Atoms/kubespray,galthaus/setup-kubernetes,ayaz/kubespray,hatch-k8s/kargo,kubernetes-incubator/kubespray,rogerwelin/kargo,kubernetes-incubator/kubespray,Atoms/kubespray,hatch-k8s/kargo,VincentS/kargo,sgm-media/kargo,Atoms/kubespray,sgm-media/kargo,Lendico/kargo,kubernetes-incubator/kargo,insequent/kargo,ayaz/kubespray,kubespray/kargo,Abdelsalam-Abbas/kubespray_fork,kubernetes-sigs/kubespray,Atoms/kubespray,kubernetes-sigs/kubespray,Lendico/kargo,kubernetes-incubator/kargo,Abdelsalam-Abbas/kubespray_fork,kubespray/kargo,galthaus/setup-kubernetes,VincentS/kargo,insequent/kargo,kubernetes-sigs/kubespray,rogerwelin/kargo