HTTP/2: add fast-path for HTTP/2 requests without request body.

Change-Id: I9a03c7f10d500e751f05c817094be41459d8017a
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Reviewed-on: https://nginx-review.googlesource.com/2830
Reviewed-by: Lizan Zhou <zlizan@google.com>

src/http/v2/ngx_http_v2.c

diff --git a/src/http/v2/ngx_http_v2.c b/src/http/v2/ngx_http_v2.c
index 11c0578..34f0dac 100644
--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -3556,7 +3556,9 @@
 
     stream = r->stream;
 
-    if (stream->skip_data) {
+    if (stream->skip_data
+        || (stream->in_closed && stream->preread == NULL))
+    {
         r->request_body_no_buffering = 0;
         post_handler(r);
         return NGX_OK;