lnchannel: rm "is_closing" method - has confusing semantics
lnchannel: rm "is_closing" method - has confusing semantics

(and there is intentional behaviour changes here, due to erroneous use of "is_closing")

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