When we rewrote Podman's pkg/spec, one of the things that was
lost was our use of a set of default environment variables, that
ensure all containers have at least $PATH and $TERM set.
While we're in the process of re-adding it, change it from a
variable to a function, so we can ensure the Join function does
not overwrite it and corrupt the defaults.
Signed-off-by: Matthew Heon <matthew.heon@pm.me>
a7e864e6e7