The use of pools.Copy avoids io.Copy's internal buffer allocation. This commit replaces io.Copy with pools.Copy to avoid the allocation of buffers in io.Copy. Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (cherry picked from commit 014095e6a07748d0e1ce2f759f5c4f4b3783e765) Signed-off-by: Andrew Hsu <andrewhsu@docker.com>