bool flag caused a panic

The task

The code on this line used to use `fmt.Sprintf("%v"....)` shenanigans [here](https://github.com/deislabs/porter/blob/main/pkg/exec/builder/flags.go#L89) to convert the key to a string to avoid yaml's typing of keys as int and bools. What's happening is that yaml is interpreting "yes" or "y" as a bool, not a string. I…