server: use buffer for proposal channel
v2_client: read whole response body before close

Client have to read whole response bodies
if they want the advantage of reusing TCP connections.

https://code.google.com/p/go/source/detail?r=d4e1ec84876c0f5611ab86a03826da14b866efb2&name=release-branch.go1.1&path=/src/pkg/net/http/transport.go
server: clear proposal wait in time