Wire-in Apache MPM module parameters and switch it

Allow to configure Apache MPM module for the containerized API/WSGI'ish
services running Apache as a backend. Change the default from 'prefork'
to 'event', which is a low level change and should provide no sensible
upgrade impact. This alleviates the related heartbeats threading issue
arising with the monkey-patched eventlet.

Merge the missing ApacheServiceBase config settings for Octavia API,
Horizon and Ironix PXE. This is needed to apply the base Apache
service hiera settings, including MPM module switches, for those
as well.

Related-bug: #1829062

Change-Id: Ia65af7a9d6ae106a61ec52912bebba72830d5f28
Signed-off-by: Bogdan Dobrelya <bdobreli@redhat.com>

deployment/nova/nova-api-container-puppet.yaml

@@ -95,6 +95,12 @@ parameters:
       e.g. { nova-context_is_admin: { key: context_is_admin, value: 'role:admin' } }
     default: {}
     type: json
+  ApacheMPMModule:
+    type: string
+    default: 'event'
+    description: Specifies the used MPM module for Apache.
+    constraints:
+      - allowed_values: ['prefork', 'event']
 
 conditions:
 
@@ -129,6 +135,7 @@ resources:
       EndpointMap: {get_param: EndpointMap}
       RoleName: {get_param: RoleName}
       RoleParameters: {get_param: RoleParameters}
+      ApacheMPMModule: {get_param: ApacheMPMModule}
       EnableInternalTLS: {get_param: EnableInternalTLS}
 
   NovaBase:

deployment/nova/nova-metadata-container-puppet.yaml

@@ -63,6 +63,12 @@ parameters:
   MonitoringSubscriptionNovaMetadata:
     default: 'overcloud-nova-metadata'
     type: string
+  ApacheMPMModule:
+    type: string
+    default: 'event'
+    description: Specifies the used MPM module for Apache.
+    constraints:
+      - allowed_values: ['prefork', 'event']
 
 conditions:
   internal_tls_enabled: {equals: [{get_param: EnableInternalTLS}, true]}
@@ -89,6 +95,7 @@ resources:
       EndpointMap: {get_param: EndpointMap}
       RoleName: {get_param: RoleName}
       RoleParameters: {get_param: RoleParameters}
+      ApacheMPMModule: {get_param: ApacheMPMModule}
       EnableInternalTLS: {get_param: EnableInternalTLS}
 
   NovaBase: