locales, models, test-environment not working without config file.

[pawelpasterz]

Describe the bug

A clear and concise description of what the bug is.
When the user runs flank with command flank android models list, a message File not found: ./flank.yml is displayed.
gcloud config file is not used as a fallback source of settings.

To Reproduce

Steps to reproduce the behavior:

1. Create a new, empty directory
2. Run flank android models list* inside newly created dir.
3. File not found: ./flank.yml

*the same is for locales, test-environment

Expected behavior

A clear and concise description of what you expected to happen.
Users should have a table of models displayed.

Details (please complete the following information):

Have you tested on the latest Flank snapshot?

Post the output of flank --version.

version: local_snapshot
revision: 052cd87

Additional context

Add any other context about the problem here.

[pawelpasterz]

@piotradamczyk5 please add more info if something is missing