add cleanCloseHandler: return from http handler immediately if remote closes
add cleanCloseHandler: return from http handler immediately if remote
closes

NebulousLabs/Sia,ChrisSchinnerl/Sia,mharkus/Sia,MrStrong/Sia,mtlynch/Sia,NebulousLabs/Sia,mharkus/Sia,ericflo/Sia,mtlynch/Sia,MrStrong/Sia,ericflo/Sia,ChrisSchinnerl/Sia