Set the proxy_read_timeout for the builder web socket to be much higher

We rarely send data from the build manager to the builder, so this should make sure nginx doesn't accidentally kill the connection

Fixes #1782

conf/nginx/server-base.conf

@@ -127,4 +127,5 @@ location ~ ^/b1/socket(/?)(.*) {
     proxy_http_version 1.1;
     proxy_set_header Upgrade $http_upgrade;
     proxy_set_header Connection "upgrade";
+    proxy_read_timeout 2000;
 }