Fix completion block not gets called if operation.isExecuting == false && operation.isCancelled == true.
Fix completion block not gets called if operation.isExecuting == false && operation.isCancelled == true.

zhangao0086/DKImagePickerController,North-American-Signs/DKImagePickerController,zhangao0086/DKImagePickerController,North-American-Signs/DKImagePickerController