fix large stderr handling without http cache
patch by Maxim Dounin
the bug has been introduced in r3461
diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index 04b01fb..12a1e81 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -1280,8 +1280,9 @@
                         } else {
                             u->buffer.pos = u->buffer.start;
                         }
+#else
+                        u->buffer.pos = u->buffer.start;
 #endif
-
                         u->buffer.last = u->buffer.pos;
                         f->large_stderr = 1;
                     }