Signature of several public methods in 'org.apache.rocketmq.namesrv.NamesrvStartup' have been changed

[caigy]

BUG REPORT

1. Please describe the issue you observed:

• What did you do (The steps to reproduce)?
  Fetch the latest develop branch.

• What is expected to see?
  Signature of public methods should be stable.

• What did you see instead?
  Several methods, like org.apache.rocketmq.namesrv.NamesrvStartup#createAndStartNamesrvController, now return void instead of previous org.apache.rocketmq.namesrv.NamesrvController. If those methods are referenced by external programs where the return values are necessary, compilation failures would be met.

2. Please tell us about your environment:

3. Other information (e.g. detailed explanation, logs, related issues, suggestions on how to fix, etc):