Fixes #195 - improved retcode handling

[jmarinaro]

This is a fix for #195

The runner client does not properly pass through exit codes from the salt master due to a mismatch of the expected data structure. The fix uses recursion to find all instances of retcode in the return data.

[nicholasmhughes]

Howdy! 👋

Apologies for the long delay on this integrating this code. We certainly appreciate your effort!

Pepper is getting some renewed focus and love, and we're checking in to see if you'd like to update this against the latest version of the base branch and ensure that all merge conditions are met.

If the items addressed by this contribution have already been fixed/added, are no longer an issue, or you no longer have a desire to work on this... please let us know and/or close out this PR.

If we don't hear from you within 7 days, we'll assume the code has been abandoned and close it out. If you'd like to revisit this in the future, you can always open a new PR.

Thank you, and we hope to see you active in the Salt ecosystem in the future!