sync: fix connection error on macOS for interleaved sync

Bug: 377538810
Test: on macos, repo sync -j64
Change-Id: I6af4d4e6669dc882f165cbb9142ad4db9b346b73
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/494241
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Kuang-che Wu <kcwu@google.com>
Tested-by: Kuang-che Wu <kcwu@google.com>

subcmds/sync.py

@@ -2582,6 +2582,7 @@ later is required to fix a server side protocol bug.
                                 callback=callback,
                                 output=pm,
                                 chunksize=1,
+                                initializer=self.InitWorker,
                             ):
                                 err_event.set()