Stream the cp operation on the client

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Replace creating buffer

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #3632 from crosbymichael/stream-cp

Stream the cp operation on the client