nginx: Move common longpolling proxy configuration into include file.

(imported from commit 4ace82824c32cec8c6da8a1a6b8a527dae105a89)

puppet/zulip/files/nginx/zulip-include/app

@@ -16,11 +16,7 @@ location /static/ {
 # Send longpoll requests to Tornado
 location ~ /json/get_events|/json/events|/api/v1/events {
     proxy_pass       http://localhost:9993;
-    include /etc/nginx/zulip-include/proxy;
-
-    # Needed for longpolling
-    proxy_buffering  off;
-    proxy_read_timeout 1200;
+    include /etc/nginx/zulip-include/proxy_longpolling;
 
     proxy_set_header X-Real-IP       $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

puppet/zulip/files/nginx/zulip-include/location-sockjs

@@ -1,8 +1,5 @@
-include /etc/nginx/zulip-include/proxy;
-
-# Needed for xhr_streaming transport
-proxy_buffering  off;
-proxy_read_timeout 1200;
+# Longpolling version needed for xhr streaming support
+include /etc/nginx/zulip-include/proxy_longpolling;
 
 proxy_set_header Upgrade         $http_upgrade;
 proxy_set_header Connection      $connection_upgrade;

puppet/zulip/files/nginx/zulip-include/proxy_longpolling

@@ -0,0 +1,3 @@
+include /etc/nginx/zulip-include/proxy;
+proxy_buffering off;
+proxy_read_timeout 1200;