lnwatcher: do not get_transaction before broadcast
lnwatcher: do not get_transaction before broadcast

this workaround was inserted to avoid losing the interface
when rebroadcasting a transaction already in the mempool
many times. but since the network should make sure we always
have a interface ready, and this problem shouldn't happen on
mainnet, remove the workaround

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