add response file uniq while loading cold cache on demand

src/http/ngx_http_file_cache.c

diff --git a/src/http/ngx_http_file_cache.c b/src/http/ngx_http_file_cache.c
index 248cd94..3233587 100644
--- a/src/http/ngx_http_file_cache.c
+++ b/src/http/ngx_http_file_cache.c
@@ -320,6 +320,7 @@
             c->node->uses = 1;
             c->node->body_start = c->body_start;
             c->node->exists = 1;
+            c->node->uniq = of.uniq;
 
             cache->sh->size += (c->length + cache->bsize - 1) / cache->bsize;
         }