fixing blocking send for sequential broadcast/recieve in core/block.go
fixing blocking send for sequential broadcast/recieve in core/block.go

mikedewar/st-core,nikhan/st-core,mikedewar/st-core,nytlabs/st-core,nikhan/st-core,nytlabs/st-core,nikhan/st-core,mikedewar/st-core,nikhan/st-core,nytlabs/st-core,nytlabs/st-core,mikedewar/st-core