Reverts https://github.com/docker/docker/pull/18197
This was a workaround before Go 1.6, not required any more.
cc @nalind @Govinda-Fichtner
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
Upstream-commit: 4d7038208f612dc0dfb0ac816adafd21043acd2f
Component: engine