Sputnik-auth database reconnection logic.

The versium.mysql plugin has been updated to allow the plugin to reconnect to a database connection that has 'gone away'. This needs to be ported to the sputnik.auth.mysql plugin.

Commit reference: 

https://github.com/yuri/sputnik/commit/872e1e938dfd6b96391ad28c60fe66409396c104
