Removed unused use statements.
Merge branch '2.2' into 2.3

* 2.2:
  [DoctrineBridge] Loosened CollectionToArrayTransformer::transform() to accept arrays
  Removed unused use statements.
  Make usleep longer and simplify assertions
  Added japanese translation resource for security component.
  [Yaml] Fixed the escaping of strings starting with a dash when dumping
  Fix in ChainLoader.php
  fixed wrong started states