Initial version of nginx parser roundtrip test

certbot-compatibility-test/nginx/nginx-roundtrip-testdata/hardwarelberrors/nginx.conf

@@ -0,0 +1,22 @@
+http {
+  geo  $lb  {
+    default      0;
+    10.1.1.1/32  1;   # LB IPs
+    10.1.1.2/32  1;
+  }
+
+  # ...
+
+  server {
+    # ...
+    access_log   /path/to/log;
+    error_page 400 /400;
+
+    location = /400 {
+      if ($lb) {
+        access_log  off;
+      }
+      return 400;
+    }
+  }
+}