daemon.on_stop: adapt to python 3.8
daemon.on_stop: adapt to python 3.8

(py3.8 has breaking changes re asyncio.CancelledError and asyncio.TimeoutError)

follow-up 308517d473d18fdc5a377e7296e0e6ab3f6c92b8

pooler/electrum-ltc,vialectrum/vialectrum,vialectrum/vialectrum,vialectrum/vialectrum,pooler/electrum-ltc,wakiyamap/electrum-mona,pooler/electrum-ltc,spesmilo/electrum,wakiyamap/electrum-mona,spesmilo/electrum,wakiyamap/electrum-mona,spesmilo/electrum,wakiyamap/electrum-mona,spesmilo/electrum,pooler/electrum-ltc