Fallback to default values from application.yaml on "spring.cloud.config.fail-fast: true"

Is your feature request related to a problem? Please describe.
As per the docs:

If you expect that the config server may occasionally be unavailable
 when your application starts, you can make it keep trying after a failure.

We want to use that, since our config server take some time to be up. But, we also want to use the application.yaml, if the server is not reachable (basically, the behaviour of spring.cloud.config.fail-fast: false).
Can we have the "best of both worlds"?

Describe the solution you'd like
When I have the spring.cloud.config.fail-fast: false set and added spring-retry and spring-boot-starter-aop to my classpath, I want to have an additional flag to indicate, that the application should fall back default values from the application.yaml

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
In the ConfigServicePropertySourceLocator is the code that checks for the fail-fast propery.

Start with ConfigServicePropertySourceLocator at the fail-fast check referenced in the issue. Review how spring.cloud.config.fail-fast, spring-retry, spring-cloud-config-client, and application.yaml currently interact. Done means defining and documenting an additional flag that retries an unavailable config server while allowing fallback to application.yaml defaults.