Merge filter and notification servers, have both tasks run on the same servers

modules/notificationserver/templates/notification.adblockplus.org.erb

 # notification.adblockplus.org
 server {
-  listen       80 default_server;
-  listen       [::]:80 default_server;
+  <% if is_default %>
+    listen 80 default_server;
+    listen [::]:80 default_server;
+  <% else %>
+    listen 80;
+    listen [::]:80;
+  <% end %>
+
   server_name  notification.adblockplus.org;
   location / {
     rewrite (.*) https://notification.adblockplus.org$1 permanent;
   }
 }
 server {
-  listen       443 ssl default_server;
-  listen       [::]:443 ssl default_server;
+  <% if is_default %>
+    listen 443 ssl default_server;
+    listen [::]:443 ssl default_server;
+  <% else %>
+    listen 443 ssl;
+    listen [::]:443 ssl;
+  <% end %>
+
   server_name  notification.adblockplus.org;
   ssl_certificate sites-available/adblockplus.org_sslcert.pem;
   ssl_certificate_key sites-available/adblockplus.org_sslcert.key;
 
   # redirect server error pages to the static page /50x.html
   #
   error_page   500 502 503 504  /50x.html;
   location = /50x.html {
     root   html;
   }
 
   location /.hg {
     internal;
   }
 
   access_log  /var/log/nginx/access_log_notification  main;
   keepalive_timeout 0;
   root   /var/www/notification;
 }