fix handling "Last-Modified" and "Accept-Ranges" for upstream responses

src/http/ngx_http_upstream.c

diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index e370196..a8cf07f 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -3301,10 +3301,11 @@
 
     *ho = *h;
 
+    r->headers_out.last_modified = ho;
+
 #if (NGX_HTTP_CACHE)
 
     if (r->upstream->cacheable) {
-        r->headers_out.last_modified = ho;
         r->headers_out.last_modified_time = ngx_http_parse_time(h->value.data,
                                                                 h->value.len);
     }
@@ -3428,6 +3429,8 @@
 
     *ho = *h;
 
+    r->headers_out.accept_ranges = ho;
+
     return NGX_OK;
 }