fix dns cannot remove domain bug

[PerforMance308]

What type of PR is this? /kind bug

What this PR does / why we need it:

Stow solution. should send dnsClusters to DNS resolver even if it is empty so that the resolver could remove unwatched domains. Which issue(s) this PR fixes: Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[hzxuzhonghu]

LG

Do we have a case covering the domain can be removed correctly

[kmesh-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Once this PR has been reviewed and has the lgtm label, please assign kevin-wangzefeng for approval. For more information see the Kubernetes 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

[PerforMance308]

added ut for checking the domain can be removed correctly

[hzxuzhonghu]

@PerforMance308 Could you update the tests and we can merge