qt tx dialog: use WaitingDialog for network requests in __init__
qt tx dialog: use WaitingDialog for network requests in __init__

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