Make credentials file take precedence over environment.

[kron4eg]

What this PR does / why we need it:
This PR aligns what docs says with the we already have: credentials file take precedence over environment. In addition it's also:

• added unit-tests

Supersedes #2881

Which issue(s) this PR fixes:
Fixes #2798

What type of PR is this?
/kind bug

Special notes for your reviewer:

Does this PR introduce a user-facing change? Then add your Release Note here:

[ACTION REQUIRED] Credentials defined in the credentials file now have precedence over credentials defined via environment variables. This change is made to match the behavior that's already documented in the KubeOne docs. If you use both the credentials file and the environment variables, we recommend double-checking your credentials file to make sure the credentials are up to date, as those credentials will be applied on the next `kubeone apply` run

Documentation:

NONE

Marking this as none, because the docs ALREADY says it's like this.

[kron4eg]

/test pull-kubeone-e2e-aws-default-install-containerd-external-v1.28.3

[kron4eg]

/test pull-kubeone-e2e-aws-default-install-containerd-external-v1.28.3

[xmudrii]

I'd make the release note action required because this is a kind of breaking change. What do you think about something like this:

[ACTION REQUIRED] Credentials defined in the credentials file now have precedence over credentials defined via environment variables. This change is made to match the behavior that's already documented in the KubeOne docs. If you use both the credentials file and the environment variables, we recommend double-checking your credentials file to make sure the credentials are up to date, as those credentials will be applied on the next `kubeone apply` run

Otherwise, this change LGTM!

[kron4eg]

I'd make the release note action required because this is a kind of breaking change. What do you think about something like this:

[ACTION REQUIRED] Credentials defined in the credentials file now have precedence over credentials defined via environment variables. This change is made to match the behavior that's already documented in the KubeOne docs. If you use both the credentials file and the environment variables, we recommend double-checking your credentials file to make sure the credentials are up to date, as those credentials will be applied on the next `kubeone apply` run

Otherwise, this change LGTM!

Funny thing is our docs states that credentials file will prevail :D

https://docs.kubermatic.com/kubeone/v1.7/guides/credentials/#credentials-file

It has the priority over the environment variables, so you can use it if you want to use different credentials or if you don’t want to export credentials as environment variables.

EDIT:
But of course despite of this, it's quite a change and we need to tell people about it!

[xmudrii]

/lgtm
/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: f685d1f5af2a4f91deaf62ff0acec58a44f66c64

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xmudrii

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