nghttpx: Don't rewrite path if http2 proxy or client proxy is enabled

There are many requests which changes its meaning when we rewrite
path.  This is due to bad percent-encoding in URI; reserved characters
are just used without percent encoding.  It seems this is common in ad
services, but I suspect more to come.  For reverse proxying situation,
sane service most likely encodes URI properly, so probably this is not
an issue.

src/shrpx_http2_upstream.cc

@@ -301,9 +301,13 @@ int Http2Upstream::on_request_headers(Downstream *downstream,
   downstream->set_request_http2_scheme(http2::value_to_str(scheme));
   downstream->set_request_http2_authority(http2::value_to_str(authority));
   if (path) {
-    auto &value = path->value;
-    downstream->set_request_path(
-        http2::rewrite_clean_path(std::begin(value), std::end(value)));
+    if (get_config()->http2_proxy || get_config()->client_proxy) {
+      downstream->set_request_path(http2::value_to_str(path));
+    } else {
+      auto &value = path->value;
+      downstream->set_request_path(
+          http2::rewrite_clean_path(std::begin(value), std::end(value)));
+    }
   }
 
   if (!(frame->hd.flags & NGHTTP2_FLAG_END_STREAM)) {

src/shrpx_https_upstream.cc

@@ -218,8 +218,12 @@ void rewrite_request_host_path_from_uri(Downstream *downstream, const char *uri,
     path += '?';
     path.append(uri + fdata.off, fdata.len);
   }
-  downstream->set_request_path(
-      http2::rewrite_clean_path(std::begin(path), std::end(path)));
+  if (get_config()->http2_proxy || get_config()->client_proxy) {
+    downstream->set_request_path(std::move(path));
+  } else {
+    downstream->set_request_path(
+        http2::rewrite_clean_path(std::begin(path), std::end(path)));
+  }
 
   std::string scheme;
   http2::copy_url_component(scheme, &u, UF_SCHEMA, uri);

src/shrpx_spdy_upstream.cc

@@ -229,8 +229,12 @@ void on_ctrl_recv_callback(spdylay_session *session, spdylay_frame_type type,
     } else {
       downstream->set_request_http2_scheme(scheme->value);
       downstream->set_request_http2_authority(host->value);
-      downstream->set_request_path(http2::rewrite_clean_path(
-          std::begin(path->value), std::end(path->value)));
+      if (get_config()->http2_proxy || get_config()->client_proxy) {
+        downstream->set_request_path(path->value);
+      } else {
+        downstream->set_request_path(http2::rewrite_clean_path(
+            std::begin(path->value), std::end(path->value)));
+      }
     }
 
     if (!(frame->syn_stream.hd.flags & SPDYLAY_CTRL_FLAG_FIN)) {