[2.5] Fix allowed failures for HHVM + MariaDB builds on Travis

Fix call on non-object in ping() with PDO wrapper

Fixes #402 (https://github.com/doctrine/DoctrineBundle/issues/402) by connecting by default to 'template1' instead of the database with the same name as the user (Postgre default in case of no dbname).

Can't use short array in php < 5.4

Add a unit-test to verify that when statements throw exceptions, the logger still has stopQuery called.

* allow hhvm/mysqli failure so poor travis can feel better