Write filter: stored delay in a variable, no functional changes.

The code is now similar to ngx_event_pipe_read_upstream().

src/http/ngx_http_write_filter_module.c

diff --git a/src/http/ngx_http_write_filter_module.c b/src/http/ngx_http_write_filter_module.c
index 83cb1fa..b19f75b 100644
--- a/src/http/ngx_http_write_filter_module.c
+++ b/src/http/ngx_http_write_filter_module.c
@@ -219,8 +219,8 @@
 
         if (limit <= 0) {
             c->write->delayed = 1;
-            ngx_add_timer(c->write,
-                          (ngx_msec_t) (- limit * 1000 / r->limit_rate + 1));
+            delay = (ngx_msec_t) (- limit * 1000 / r->limit_rate + 1);
+            ngx_add_timer(c->write, delay);
 
             c->buffered |= NGX_HTTP_WRITE_BUFFERED;