Avoid Ruby 2.0 warnings when running tests

When running the tests with `rake`, the following errors are issued:

```bash
/Users/hanke/temp/redis-rb/test/distributed_remote_server_control_commands_test.rb:22: warning: shadowing outer local variable - info
/Users/hanke/temp/redis-rb/test/publish_subscribe_test.rb:71: warning: assigned but unused variable - listening
```

I rewrote the tests such that these warnings are not issued anymore. Tests still run: `476 tests, 1782 assertions, 0 failures, 0 errors, 0 skips`.

Cheers!