Use `error`, `warn`, `verbose`, or `silly` to replace `info` for our log level

[huan]

I saw we are using lots of log.info(...) in the puppet code, which is not a necessary message to the end users.

We should:

1. Use warn when there's something we need the user to notice
2. Use error when there's any error
3. Use verbose for tracking the methods (always be the first call inside a method)
4. Use silly to output more debug information.

NEVER use info inside a puppet.

Thank you very much.