Updates server_group for 2.0.0

Replaces the policies argument with policy. The policies attribute is
ancient and was superceded by policy a long time ago[0][1]. Since policy and
policies differ in type, we can't simply alias these and had to drop
policies to keep the implementation small.

[0] https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id59
[1] https://docs.openstack.org/api-ref/compute/#create-server-group

Change-Id: Icd658fb179ca0a96276b033130b9dddfedd84236

ci/roles/server_group/defaults/main.yml

@@ -0,0 +1,11 @@
+expected_fields:
+  - id
+  - name
+  - policy
+  - policies
+  - member_ids
+  - metadata
+  - project_id
+  - rules
+  - user_id
+

ci/roles/server_group/tasks/main.yml

@@ -0,0 +1,72 @@
+- name: Create server group
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    policy: affinity
+  register: server_group
+
+- name: Assert changed
+  assert:
+    that: server_group is changed
+
+- name: Assert return values
+  assert:
+    that: item in server_group.server_group
+  loop: "{{ expected_fields }}"
+
+- name: Create server group again
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    policy: affinity
+  register: server_group
+
+- name: Assert not changed
+  assert:
+    that: server_group is not changed
+
+- name: Delete server group
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    state: absent
+  register: server_group
+
+- name: Assert changed
+  assert:
+    that: server_group is changed
+
+- name: Delete server group again
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    state: absent
+  register: server_group
+
+- name: Assert not changed
+  assert:
+    that: server_group is not changed
+
+- name: Create server group with rules
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    policy: anti-affinity
+    rules:
+      max_server_per_host: 2
+  register: server_group
+
+- name: Assert changed
+  assert:
+    that: server_group is changed
+
+- name: Assert return values
+  assert:
+    that: item in server_group.server_group
+  loop: "{{ expected_fields }}"
+
+- name: Delete server group
+  openstack.cloud.server_group:
+    cloud: "{{ cloud }}"
+    name: ansible_group
+    state: absent