bugfix: `spack config get <section>` in environments
bugfix: `spack config get <section>` in environments

`spack config get <section>` was erroneously returning just the `spack.yaml`
for the environment.

It should return the combined configuration for that section (including
anything from `spack.yaml`), even in an environment.

- [x] reorder conditions in `cmd/config.py` to fix

LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack,LLNL/spack