Disable debugging (for kbfs)

I recently noticed that my `keybase.kbfs.log` and `keybase.service.log` files were nearing around 100MB in size, each. It appears that both contain quite a bit of [DEBU ] statements.

When I run `keybase -d status` I can see that kbfs is started with the debug flag: `/Applications/Keybase.app/Contents/SharedSupport/bin/kbfs -debug -log-file=/Users/crahan/Library/Logs/keybase.kbfs.log`

Is there a way to disable this debug flag? Can we add `--no-debug` to the master `config.json` file to help prevent this. If so, can someone provide an example?

Start with the master config.json handling and the kbfs command shown by `keybase -d status`. Trace how the debug flag is selected and how configuration reaches kbfs. Done means the configuration provides a documented way to avoid starting kbfs in debug mode and the resulting logs no longer contain the unwanted debug output.

Written by the indexing model from the issue text.