MigrationsCollector still requires a active connection

Collector still requires an configure connection.
When starting new project and database is not yet configured, MigrationsCollector is trying to connect to database and because of PDO timeout, page feels are hanged.

Ref.:
https://github.com/doctrine/DoctrineMigrationsBundle/pull/428
https://github.com/doctrine/DoctrineMigrationsBundle/issues/423