Fixed incorrect namespace for doctrine connection manager

[edefimov]

Liip monitor is using old class Doctrine\Common\Persistence\ConnectionRegistry for performing doctrine DBAL checks. This class has been moved to another namespace since doctrine/persistence:^1.3.

This PR fixes old namespace and lets the liip monitor bundle work with both 1.3.x and 2.x branches of doctrine/persistence.

[kbond]

Thanks @edefimov.

[jmalinens]

thanks @edefimov @kbond any chance to create new tag? many users are updating to newer doctrine and old namespaces are removed there making liipmonitor bundle unusable

[kbond]

Sure! 2.14.0