TF: preserve environment variables on ssh login

We're using docker with sshd. ENV aren't preserved.
In addition, it keeps the environment variables settings in a single
place, within the docker image itself.

Signed-off-by: Fathi Boudra <fathi.boudra@linaro.org>
Change-Id: I06005c608c2e6c6a22c0ed1acf4b84addcee22fc
4 files changed