Function find() in DockerApplication `initialize` method
returned `null` due to the fact that instance of DockerRedisSlave
class was created with `new()` and this object didn't have owner.
This fix corrects the creation of object
Change-Id: Ib4209cd95edb0209f82dc05e55fe777a212ec9e5
Closes-Bug: #1560441
39875b0e75