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

modules/filterserver/templates/easylist-downloads.adblockplus.org.erb

 server {
-  listen 80 default_server;
-  listen [::]:80 default_server;
-  listen 443 ssl default_server;
-  listen [::]:443 ssl default_server;
+  <% if is_default %>
+    listen 80 default_server;
+    listen [::]:80 default_server;
+    listen 443 ssl default_server;
+    listen [::]:443 ssl default_server;
+  <% else %>
+    listen 80;
+    listen [::]:80;
+    listen 443 ssl;
+    listen [::]:443 ssl;
+  <% end %>
 
   server_name easylist-downloads.adblockplus.org easylist-msie.adblockplus.org;
   access_log /var/log/nginx/access_log_easylist_downloads  main;
   root /var/www/easylist;
   keepalive_timeout 0;
   charset utf-8;
   gzip_static on;
   default_type text/plain;
 
   ssl_certificate sites-available/easylist-downloads.adblockplus.org_sslcert.pem;
   ssl_certificate_key sites-available/easylist-downloads.adblockplus.org_sslcert.key;
 
   set $id "$scheme:$http_host";
   if ($id = "http:easylist-downloads.adblockplus.org") {
     rewrite (.*) https://$http_host$1 permanent;
   }
 
   error_page 403 404 https://easylist.adblockplus.org/;
 
   # redirect server error pages to the static page /50x.html
   #
   error_page   500 502 503 504  /50x.html;
   location = /50x.html {
     root   html;
   }
 }