tests: fix test_lnpeer.test_payment_race
tests: fix test_lnpeer.test_payment_race

broke in https://github.com/spesmilo/electrum/commit/b6b13217b4929c5701e18a1310b20caf01fb61e5
see changes to lnworker.htlc_fulfilled

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