missing setup in gasless_test.go

[bap2pecs]

right now it only sets DefaultMinGasPriceAllowed and EnableL2SuggestedGasPricePolling

but I think DefaultGasPriceWei also needs to be set to 0

or else I will get

ERROR   claimtxman/claimtxman.go:422   failed to send tx 0x... to network: insufficient funds for gas * price + value