correctly validate service-name-mapping parameter

[aruato]

What is the purpose of the change?

The service-name-mapping is set as follows:

if (SERVICE_REGISTRY_PROTOCOL.equals(registryURL.getProtocol())) {
url = url.addParameterIfAbsent(SERVICE_NAME_MAPPING_KEY, "true");
}

The validation logic should be consistent with the setting logic.

Checklist

• Make sure there is a GitHub_issue field for the change.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Make sure gitHub actions can pass. Why the workflow is failing and how to fix it?