Fix host used to configure HA groups

When the role is run with `--limit nodes_without_first_node`, the HA
groups are not configured (tasks are skipped). Use `_init_node` instead
of `groups[pve_group][0]` to run the tasks.

`_init_node` is any active node in an already initialized Proxmox
cluster which is part of the run.

tasks/pve_cluster_config.yml

@@ -80,7 +80,7 @@
   proxmox_query:
     query: "/cluster/ha/groups"
   register: _ha_group_list
-  when: "inventory_hostname == groups[pve_group][0]"
+  when: "inventory_hostname == _init_node"
 
 - name: Create PVE cluster HA groups
   command: >-
@@ -94,15 +94,15 @@
     -restricted {{ item.restricted }}
     {% endif %}
   when:
-    - "inventory_hostname == groups[pve_group][0]"
+    - "inventory_hostname == _init_node"
     - item.name not in _ha_group_list.response | json_query("[*].group")
   with_items: "{{ pve_cluster_ha_groups }}"
 
 - name: Update PVE cluster HA groups
   command: >-
     ha-manager groupset {{ item.0.name }} -{{ item.1 }} "{{ item.0[item.1] }}"
   when:
-    - "inventory_hostname == groups[pve_group][0]"
+    - "inventory_hostname == _init_node"
     - item.0.name in _ha_group_list.response | json_query("[*].group")
     - item.1 in item.0
     - item.0[item.1] != _ha_group_list.response