Workaround upstream issue with apache2_module

The apache2_module module in Ansible 2.2 is much more strict around
configuration syntax checks and contains a bug [0] preventing MPM
modules from being changed.

Move the enabling of apache2 modules ahead of writing configurations and
temporarily use the command module to enable/disable apache2 modules
until this issue is resolved.

[0] https://github.com/ansible/ansible-modules-core/issues/5328

Change-Id: I65ffc016b594ebe0d61d1355364d222d0082ee63

tasks/horizon_apache.yml

@@ -13,6 +13,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Workaround for https://github.com/ansible/ansible-modules-core/issues/5328
+# TODO: Replace using apache2_module when fixed in Ansible release
+- name: Enable apache2 modules
+  command: "{{ (item.state == 'present') | ternary('a2enmod','a2dismod') }} {{ item.name }}"
+  register: horizon_apache2_module
+  changed_when: horizon_apache2_module.stdout.find('{{ item.name }} already') == -1
+  with_items:
+    - { state: present, name: wsgi }
+    - { state: present, name: ssl }
+    - { state: absent, name: mpm_event }
+    - { state: present, name: mpm_worker }
+    - { state: present, name: rewrite }
+    - { state: present, name: headers }
+  notify: Restart apache2
+
 - name: Drop apache2 configs
   template:
     src: "{{ item.src }}"
@@ -34,19 +49,6 @@
     - { state: absent, name: 000-default.conf }
   notify: Restart apache2
 
-- name: Enable apache2 modules
-  apache2_module:
-    state: "{{ item.state }}"
-    name: "{{ item.name }}"
-  with_items:
-    - { state: present, name: wsgi }
-    - { state: present, name: ssl }
-    - { state: absent, name: mpm_event }
-    - { state: present, name: mpm_worker }
-    - { state: present, name: rewrite }
-    - { state: present, name: headers }
-  notify: Restart apache2
-
 - name: Ensure Apache ServerName
   lineinfile:
     dest: "/etc/apache2/apache2.conf"