Explicitly require wsgi to be enabled in apache2

PROD-32552

Change-Id: I027ffc35c5a09081a8bd565067cdea234e054666
diff --git a/apache/server/site/nova-placement.yml b/apache/server/site/nova-placement.yml
index a869fea..a911fa2 100644
--- a/apache/server/site/nova-placement.yml
+++ b/apache/server/site/nova-placement.yml
@@ -12,6 +12,8 @@
     server:
       enabled: true
       default_mpm: event
+      modules:
+        - wsgi
       site:
         nova_placement:
           enabled: false