Improve routing between containers

Create user network nginx-internal
and use Docker's internal DNS server
to resolve containers by hostname.

roles/nginx/templates/nginx.conf.j2

@@ -26,6 +26,7 @@ http {
     keepalive_timeout  65;
 
     #gzip  on;
+    resolver 127.0.0.11 valid=30;
     ssl_certificate /etc/nginx/{{ base_domain }}.crt;
     ssl_certificate_key /etc/nginx/{{ base_domain }}.key;
     include /etc/nginx/conf.d/*.conf;