add ROUTER_SLOWLORIS_TIMEOUT enviroment variable to default router image

Using the HAProxy router to impliement basic DDOS protection. When the
enviroment variable ROUTER_SLOWLORIS_TIMEOUT is set it limits the amount
of time a client has to send their whole HTTP request or HAProxy will
shut down the connection

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1328037

Author: JacobTanenbaum

images/router/haproxy/conf/haproxy-config.template

@@ -38,6 +38,9 @@ defaults
 {{ if ne (env "ROUTER_SYSLOG_ADDRESS" "") ""}}
   option httplog
   log global
+{{ end }}
+{{ with (env "ROUTER_SLOWLORIS_TIMEOUT" "") }}
+  timeout http-request {{.}}
 {{ end }}
   timeout connect 5s
   timeout client 30s