Add variable to override keypair setup python interpreter

When using a non-standard host for keypair setup (such as a utility
container) it is necessary to set a custom python interpreter
which has access to openstacksdk.

This commit provides a variable to do this in the same style as
used for service setup hosts.

Depends-On: https://review.opendev.org/c/openstack/openstack-ansible/+/777601
Change-Id: Ia2056cf287b666d4d3d8d36f06772c5117ca6bf7

defaults/main.yml

@@ -253,7 +253,8 @@ octavia_security_group_rule_cidr:
 # ssh enabled - switch to True if you need ssh access to the amphora
 octavia_ssh_enabled: False
 octavia_ssh_key_name: octavia_key
-octavia_keypair_setup_host: "{{ openstack_keypair_setup_host | default('localhost') }}"
+octavia_keypair_setup_host: "{{ openstack_service_setup_host | default('localhost') }}"
+octavia_keypair_setup_host_python_interpreter: "{{ openstack_service_setup_host_python_interpreter | default((octavia_keypair_setup_host == 'localhost') | ternary(ansible_playbook_python, ansible_python['executable'])) }}"
 # port the agent listens on
 octavia_agent_port: "9443"
 octavia_health_manager_port: 5555

tasks/octavia_keypair.yml

@@ -16,8 +16,7 @@
 - name: Create keypair for Octavia
   delegate_to: "{{ octavia_keypair_setup_host }}"
   vars:
-    ansible_python_interpreter: >-
-      {{ (octavia_keypair_setup_host == 'localhost') | ternary(ansible_playbook_python, ansible_python['executable']) }}
+    ansible_python_interpreter: "{{ octavia_keypair_setup_host_python_interpreter }}"
   block:
     - name: Create keypair
       register: _octavia_keypair