pulumilocal not working with --cwd option

[cabeaulac]

pulumilocal is writing output to the Pulumi.<stack>.yaml file. When you run the pulumi command with the --cwd command to change directories, the Stack yaml file is written to the wrong location.

Change this code to not write directly to the Pulumi stack yaml file. This is brittle and could break when the file structure changes. Instead, use the following command to set all of the configuration:

pulumi config set-all (vars)

Do this before any call to pulumi [up, destroy, preview, cancel]