Correct authentication and token generation v3 api

1. Remove a wrong route mapper for '/v3/tokens' path.
2. Correct NOAUTH list to include path of authentication and token
generation v3 api.
3. Correct authentication implementation of the api.
Merge pull request #152 from LiuZhiyan/correct-v3-auth-token-gen-api

Correct authentication and token generation v3 api