interface: validate protocol-version negotiation on client-side too
interface: validate protocol-version negotiation on client-side too

related: https://github.com/romanz/electrs/issues/314

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