functional test use mysql

I found a mysql maven plugin. It's able to download a mysql distribution and unpack it for use in integration test. Now we can mimic real production environment for testing. 

*note*:
Seems like if you already have mysql installed and running. Even if the port number is different, it still reuses the same server. On Jenkins we have credential for root account. Therefore we need to create a separate user (I use zanata/zanata) for running the test.

```
CREATE USER 'zanata'@'localhost' IDENTIFIED BY 'zanata';
GRANT ALL ON zanata_functional.* TO 'zanata'@'localhost';
```