* Make the exiting node check piece hashes, piece IDs, and piece hash signatures before relaying successful transfer data to the satellite.
* Enable immediate graceful exit failure for "successful" transfers that fail satellite-side validation.
* Move transfer piece logic in storagenode worker to separate function (to make the worker easier to understand)
all of the packages and tests work with both grpc and
drpc. we'll probably need to do some jenkins pipelines
to run the tests with drpc as well.
most of the changes are really due to a bit of cleanup
of the pkg/transport.Client api into an rpc.Dialer in
the spirit of a net.Dialer. now that we don't need
observers, we can pass around stateless configuration
to everything rather than stateful things that issue
observations. it also adds a DialAddressID for the
case where we don't have a pb.Node, but we do have an
address and want to assert some ID. this happened
pretty frequently, and now there's no more weird
contortions creating custom tls options, etc.
a lot of the other changes are being consistent/using
the abstractions in the rpc package to do rpc style
things like finding peer information, or checking
status codes.
Change-Id: Ief62875e21d80a21b3c56a5a37f45887679f9412
