Fix cli being ran twice

server-main.js runs itself outside a code-server context, which is
determined using the CODE_SERVER_PARENT_PID environment variable.  This
is set by the wrapper, but there is no wrapper when running the
cli (only for the server), so this resulting in the cli running
twice (one self-run on initial import, again when we run spawnCli).

This might fix https://github.com/coder/code-server/issues/7042