Add warn about using the ignored --mount option

[henry3260]

fix #21291

We have 2 cases:

• --mount: user expects to have HOME mounted in the guest. This does nothing and we want to show an example how to mount a specific directory in the guest.
• --mount --mount-string ...: warn that the --mount flag is ignored and can be removed

After:

First Case:

Second Case:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: henry3260
Once this PR has been reviewed and has the lgtm label, please assign comradeprogrammer for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @henry3260. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[minikube-bot]

Can one of the admins verify this patch?

[medyagh]

I think instead of warnining, we should merge the
--mount
and
--mount-string flags into

--mount

and if ppl enter --mount true --mount-string /blahblah:/blahblah

we could still support it
with good unit testing we could just transition into "--mount " flag without breaking old syntax users