[PATCH 4 of 7] test-graft: add a missing output line for Windows

[Matt Harbison]

# HG changeset patch
# User Matt Harbison <matt_harbison at yahoo.com>
# Date 1534610147 14400
#      Sat Aug 18 12:35:47 2018 -0400
# Node ID aee8ed1bbd3280214d55cef2b41a810fd48480e4
# Parent  037f5c3894abad5e702cbfb182e8301565b5a173
test-graft: add a missing output line for Windows

diff --git a/tests/test-graft.t b/tests/test-graft.t
--- a/tests/test-graft.t
+++ b/tests/test-graft.t
@@ -710,6 +710,7 @@ Transplants of grafts can find a destina
   resolving manifests
    branchmerge: True, force: True, partial: False
    ancestor: b592ea63bb0c, local: 7e61b508e709+, remote: 7a4785234d87
+  starting 4 threads for background file closing (?)
   committing files:
   b
   warning: can't find ancestor for 'b' copied from 'a'!