Before 3.5.x, users define zoo.cfg with "clientPort" parameter which is used to identify on which port the server is serving clients.
After upgrading to 3.5.x, the new format:
force users to define all the client ports on the entire ZK ensemble.
The goal of this issue is to preserve backward compatibility upgrading 3.4 to 3.5.
1. when a user defines an old-style config file, it should function the same as the old way – It should use clientPort variable and shouldn't create a dynamic file.
2. when a user with old-style config file tries to do reconfig relevant jobs, it should stop him and give out a warning.