wireprotov2peer: wait for initial object before resolving future
As part of rolling out wireprotov2 with redirect support, I
encountered an edge case with regards to future resolution.
Essentially, the initial response frame from the server did not
fully decode the initial CBOR object. The frame wasn't marked as
EOS. In the previous code, we resolved the future for the request
to response.objects(), which mapped to the commandresponse instance
which would eventually produce a redirect. Upon receiving
subsequent data, the initial CBOR object containing the redirect
would be decoded and we'd process the redirect. However, the
future would already have been resolved with the initial
commandresponse.objects() and the client iterating over the
objects wouldn't receive any objects from the redirect because
the redirect was populating a different commandresponse instance!
This commit changes the logic so we don't resolve futures until
the initial CBOR response object is fully decoded or until EOS
occurs. In cases where there is an empty or partial frame
associated with a redirect, the future will now resolve with the
commandresponse containing the proper series of decoded objects.