These two operations are called when docker tries to store and delete
credentials (docker login and docker logout) respectively. This change
makes it so that both of these operations are implemented as nops
instead of returning a "not implemented" error.

The goal here is to ensure compatibilities with applications and tools
that call docker login or docker logout for the user as part of their
normal operations.

Co-authored-by: Gavin Inglis <43075615+ginglis13@users.noreply.github.com>

…login

With the new capability to opt-out of saving credentials, we can guide
users to not to save ecr credentials by setting the
AWS_ECR_IGNORE_CREDS_STORAGE environment variable when encountering the
`notImplemented` error.

Ref:
https://docs.aws.amazon.com/cli/latest/reference/ecr/get-login-password.html

This change fixes an incorrect use of the test's scope. The parent
was used for assertions and setting the env. This now should be using
the correct instance of the `*testing.T` for the test.