[Enhancement] Add test code for this module [eventmesh-sdk-java]

### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/eventmesh/issues?q=is%3Aissue) and found no similar issues.

### Enhancement Request

Add test code for the grpc of the eventmesh-sdk-java module.

### Describe the solution you'd like

Module name: eventmesh-sdk-java
located in: eventmesh-sdks/eventmesh-sdk-java
Task status: ×(unfinished) / √(finished)

> Notes: This issue will not be closed, if you want to submit a PR to do some unit tests on this module or select some of the following classes to do some unit tests, please submit a detailed issue separately and linked to the PR you submitted.

Unit test coverage:


### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!