[ISSUE #73] Support mounting a configMap to rocketmq dashboard

[drivebyer]

What is the purpose of the change

inherit #132

Brief changelog

XX

Verifying this change

XXXX

Please go through this checklist to help us incorporate your contribution quickly and easily.

Notice: It would be helpful if you could finish the following checklist (the last one is not necessary) before request the community to review your PR.

• Make sure there is a Github issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a Github issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [ISSUE #123] Fix UnknownException when host config not exist. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Check RBAC rights for Kubernetes roles.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist.
• Run make docker-build to build docker image for operator, try your changes from Pod inside your Kubernetes cluster, not just locally. Also provide screenshots to show that the RocketMQ cluster is healthy after the changes.
• Before committing your changes, remember to run make manifests to make sure the CRD files are updated.
• Update documentation if necessary.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

[caigy]

LGTM