Add shell_out_with_systems_locale to ShellOut

In the spirit of moving away from Command in favor of ShellOut, I've included a `shell_out_with_systems_locale`, which mimics the behavior of `run_command_with_systems_locale`.

Once this is merged, https://github.com/opscode/chef/pull/1532 can be updated to use ShellOut (I have already done that work and have manually verified the changes work on Debian 7).

\cc @opscode/client-eng 
yeah here you're missing the before block to explicitly clear LC_ALL, so you're just inheriting whatever I've got when I run rspec?