wallet_test: add tests exercising output locking for concurrent safe funding
wallet_test: add tests exercising output locking for concurrent safe funding

LightningNetwork/lnd,aakselrod/lnd,ddustin/lnd,LightningNetwork/lnd,BitfuryLightning/lnd,aakselrod/lnd,AndrewSamokhvalov/lnd,bryanvu/lnd,BitfuryLightning/lnd,ddustin/lnd,bryanvu/lnd,AndrewSamokhvalov/lnd