Use SSH key defined by ssh_key_path when connecting to Ansible control host

This avoids problems such as "Too many authentication failures" when
using SSH agent.

Author: markgoddard

ansible/vars/defaults.yml

@@ -18,6 +18,8 @@ vault_password_path: "~/vault.password"
 
 ssh_key_path:
 
+ansible_ssh_private_key_file: "{{ ssh_key_path }}"
+
 vxlan_vni:
 
 root_domain: stackhpc.com