Force LANG=C before appending rest of environment

It seems that go ```Command``` only overrides an environment variable with the first value seen in the ```Env``` array, so if ```os.Environ()``` already has ```LANG``` set, the other appended value is ignored. This causes problems as not being able to correctly parse the ifconfig output to retrieve the host IP.

This pull request reorders how Env is built, fixing this problem.