dl: race in piceHashers at shutdown

[AskAlexSharov]

==================
WARNING: DATA RACE
Read at 0x00c00f8c2310 by goroutine 934:
  github.com/anacrolix/torrent.(*Torrent).processHashResults()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:2890 +0x30a
  github.com/anacrolix/torrent.(*Torrent).tryCreateMorePieceHashers.func1.gowrap2()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:2776 +0x33

Previous write at 0x00c00f8c2310 by goroutine 42872:
  github.com/anacrolix/torrent.(*Torrent).close()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:1112 +0x5b2
  github.com/anacrolix/torrent.(*Client).Close()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/client.go:444 +0x10c
  github.com/erigontech/erigon-lib/downloader.(*Downloader).Close()
      /home/ubuntu/erigon/erigon-lib/downloader/downloader.go:2766 +0x118
  github.com/erigontech/erigon/eth.(*Ethereum).Stop()
      /home/ubuntu/erigon/eth/backend.go:1586 +0x104
  github.com/erigontech/erigon/node.(*Node).stopServices()
      /home/ubuntu/erigon/node/node.go:221 +0x148
  github.com/erigontech/erigon/node.(*Node).Close()
      /home/ubuntu/erigon/node/node.go:164 +0x1b7
  github.com/erigontech/erigon/turbo/debug.ListenSignals.gowrap2()
      /home/ubuntu/erigon/turbo/debug/signal.go:46 +0x42

Goroutine 934 (running) created at:
  github.com/anacrolix/torrent.(*Torrent).tryCreateMorePieceHashers.func1()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:2776 +0x216
  github.com/anacrolix/torrent.(*Torrent).tryCreateMorePieceHashers()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:2778 +0x57
  github.com/anacrolix/torrent.(*Torrent).onSetInfo()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:602 +0x5f7
  github.com/anacrolix/torrent.(*Torrent).setInfoBytes()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:638 +0x8f
  github.com/anacrolix/torrent.(*Torrent).SetInfoBytes()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/torrent.go:1915 +0x110
  github.com/anacrolix/torrent.(*Torrent).MergeSpec()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/client.go:1485 +0xd4
  github.com/anacrolix/torrent.(*Client).AddTorrentSpec()
      /home/ubuntu/go/pkg/mod/github.com/erigontech/torrent@v1.54.2-alpha-33/client.go:1470 +0x1ba
  github.com/erigontech/erigon-lib/downloader._addTorrentFile()
      /home/ubuntu/erigon/erigon-lib/downloader/util.go:340 +0xa9d
  github.com/erigontech/erigon-lib/downloader.addTorrentFile()
      /home/ubuntu/erigon/erigon-lib/downloader/util.go:317 +0x284
  github.com/erigontech/erigon-lib/downloader.(*Downloader).addTorrentFilesFromDisk.func2()
      /home/ubuntu/erigon/erigon-lib/downloader/downloader.go:2735 +0x10a
  golang.org/x/sync/errgroup.(*Group).Go.func1()
      /home/ubuntu/go/pkg/mod/golang.org/x/sync@v0.7.0/errgroup/errgroup.go:78 +0x91

Goroutine 42872 (running) created at:
  github.com/erigontech/erigon/turbo/debug.ListenSignals()
      /home/ubuntu/erigon/turbo/debug/signal.go:46 +0x377
  github.com/erigontech/erigon/node.StartNode.gowrap1()
      /home/ubuntu/erigon/node/node.go:423 +0x5d
==================