AddWritePermSubCommandTest uses fixed port that may not be available

[lizhanhui]

Tests in error:
org.apache.rocketmq.tools.command.namesrv.AddWritePermSubCommandTest.testExecute(org.apache.rocketmq.tools.command.namesrv.AddWritePermSubCommandTest)
Run 1: AddWritePermSubCommandTest.testExecute » Bind Address already in use
Run 2: AddWritePermSubCommandTest.after:50 NullPointer

[lizhanhui]

Observed in https://github.com/apache/rocketmq/actions/runs/3224766162/jobs/5278048038

[echooymxq]

@lizhanhui In RocketMQ, There are others tests also use fixed port. Has the community considered using testcontainer to Integration Test ? 😯

[lizhanhui]

For test cases, best to use OS pick-up available port.