Fixed MySQL support for puppet-jira

When I pulled your puppet-jira module into my production setup with MySQL I noticed that while almost everything worked out of the box when setting parameters in the node definition unfortunately MySQL didn't quite work.  When I went digging I discovered that the example YAML file for hiera (which I then decided to switch to) was also out-of-date with reference to your new variable names.  I updated the variable names to what works on my production setup (verified works great now) and I also updated your dbconfig MySQL template file so now it appropriately fills the name of the dbdriver whereas before it was referencing the now-uninitialized variable jira_dbdriver, hence making the file blank.

With the below mods your module works awesome out of the box on my setup (though of course you need to grab the MySQL driver JAR yourself, but that's expected and noted already).