Use Interface instead of lister/informer in controller

[Jeffwan]

A follow up PR of #155

In the common code base, we still use low level listers and hasSynced which is not used in training-operator any more.
Let's change to XXInterface from kubeClientSet. Otherwise, we have to create sharedInformers and then create listers which is unnecessary in latest client pattern

[zw0610]

Good idea. May I assign this feature to myself?

[Jeffwan]

/assign @zw0610

[Jeffwan]

@zw0610 sure. Feel free to pick it up