fix TestUnitSigning determinism
fix TestUnitSigning determinism

mtlynch/Sia,ChrisSchinnerl/Sia,NebulousLabs/Sia,johnathanhowell/Sia,MrStrong/Sia,ericflo/Sia,rivine/rivine,mharkus/Sia,MrStrong/Sia,rivine/rivine,mharkus/Sia,ericflo/Sia,mnsl/Sia,mnsl/Sia,ChrisSchinnerl/Sia,NebulousLabs/Sia,mtlynch/Sia