Increase perip limit_req_zone map size

roles/float-infra-nginx/templates/config/conf.d/limits.conf

 # Per-IP rate limiting.
-limit_req_zone $binary_remote_addr zone=perip:32m rate={{ nginx_limit_perip_rate }};
+# A 128M zone holds information on about 1M IPs.
+limit_req_zone $binary_remote_addr zone=perip:128m rate={{ nginx_limit_perip_rate }};
 # Per-server rate limiting.
 limit_req_zone $server_name zone=perserver:10m rate={{ nginx_limit_perserver_rate }};