Explicitly require wsgi to be enabled in apache2

PROD-32552

Change-Id: I027ffc35c5a09081a8bd565067cdea234e054666
diff --git a/apache/server/site/barbican.yml b/apache/server/site/barbican.yml
index 7a4297b..efa1ffd 100644
--- a/apache/server/site/barbican.yml
+++ b/apache/server/site/barbican.yml
@@ -8,6 +8,9 @@
   apache:
     server:
       enabled: true
+      default_mpm: event
+      modules:
+        - wsgi
       site:
         barbican:
           enabled: false