This removes the incomplete symlink handling from engine.go and it adds
it one place in docker.go.
It also enables handling symlinks for TMPDIR.
Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Upstream-commit: 611acf7a7c1c3a6796e862fb94143890a9aa4573
Component: engine