lighthttpd: don't remove envvars
As this is running inside a controlled environment, we don't need to scrub the environment variables.
This also allows passing through any user-set variables (using the envvars service).
Bug: T354320 Signed-off-by: David Caro me@dcaro.es Change-Id: I3364b7a0cb4a9ce6cbcef026164874da943f797a