test_mpp_split: add tests for exclude_single_part_payments=False
test_mpp_split: add tests for exclude_single_part_payments=False

spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,pooler/electrum-ltc,spesmilo/electrum,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum