connector: auto upgrade the db if sqlite is used

Reasons for not upgrading automatically is:
- in multimaster deployment, several upgrade could happen at the same time
- for big production env, upgrading should be taken seriously:
  - set  the front end proxy in maintainance mode
  - stop all instances,
  - backup old db
  - do the upgrade
  - start all instance back

Reasons for upgrading automatically are:
  - for smaller instance above reasons are not applicable