Ensure that selected Apache MPM is enforced

At the moment services might have different MPM selected while all
operating the same Apache setup, ie on metal setup.
This results in failures to set selected MPMs, so eventually second run
of roles after initial deployment will end up in failure (ie upgrade).

This patch ensures that all except selected MPMs are disabled and do
role get's the desired state of deployment.

We also need to align selected MPM across all roles to avoid
future conflicts.

Depends-On: https://review.opendev.org/c/openstack/openstack-ansible/+/929892
Change-Id: I3288c6e4060fe954b2c2725865783aa18bf6bc0d

defaults/main.yml

@@ -142,6 +142,9 @@ skyline_pip_packages:
       )
     }}"
 
+## Apache configuration
+skyline_apache_mpm_backend: "{{ openstack_apache_mpm_backend | default('event') }}"
+
 ## Service Name-Group Mapping
 skyline_services:
   skyline-api:

tasks/skyline_apache.yml

@@ -13,6 +13,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Ensure apache2 MPM for Debian/Ubuntu
+  apache2_module:
+    name: "{{ item.name }}"
+    state: "{{ item.state }}"
+    ignore_configcheck: yes
+    warn_mpm_absent: false
+  with_items: "{{ skyline_apache_mpms | sort(attribute='state') }}"
+  when:
+    - ansible_facts['pkg_mgr'] == 'apt'
+  notify: Restart web server
+
+- name: Ensure apache2 MPM for EL
+  copy:
+    content: |
+      LoadModule mpm_{{ skyline_apache_mpm_backend }}_module modules/mod_mpm_{{ skyline_apache_mpm_backend }}.so
+
+    dest: /etc/httpd/conf.modules.d/00-mpm.conf
+    mode: "0644"
+  when:
+    - ansible_facts['pkg_mgr'] == 'dnf'
+  notify: Restart web server
+
 - name: Enable apache2 modules
   apache2_module:
     name: "{{ item.name }}"

vars/debian.yml

@@ -25,13 +25,17 @@ skyline_distro_packages:
 skyline_system_service_name: apache2
 skyline_vhost_enable_path: /etc/apache2/sites-enabled
 
+skyline_apache_mpms:
+  - name: "mpm_event"
+    state: "{{ (skyline_apache_mpm_backend == 'event') | ternary('present', 'absent') }}"
+  - name: "mpm_worker"
+    state: "{{ (skyline_apache_mpm_backend == 'worker') | ternary('present', 'absent') }}"
+  - name: "mpm_prefork"
+    state: "{{ (skyline_apache_mpm_backend == 'prefork') | ternary('present', 'absent') }}"
+
 skyline_apache_modules:
   - name: "ssl"
     state: "present"
-  - name: "mpm_event"
-    state: "absent"
-  - name: "mpm_worker"
-    state: "present"
   - name: "rewrite"
     state: "present"
   - name: "headers"