lnpeer: move ping_if_required away from message_loop
lnpeer: move ping_if_required away from message_loop

If our connection dies because we went to sleep, message_loop
will stall and ping_if_required will never be called.

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