Update cifar10_input.py to work through on version 0.12.0-rc1

[un-knight]

I'm working with models/tutorials/image/cifar10/.

There is an error strided_slice() missing 1 required positional argument: 'strides' when I run the command python cifar10_train.py under the version of 0.12.0-rc1. Although the document said strides is optional.

So I replaced strided_slice with slice to make it work as a temporary solution.

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[un-knight]

I signed it

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CLAs look good, thanks!

[daviddao]

Might that be a better solution: http://stackoverflow.com/questions/41195121/tensorflow-strided-slice-missing-argument-strides ? (instead of using tf.slice())

[un-knight]

Hi! @daviddao, I can't say which one is better, though I had thought about both of the solutions. But the reason why I PR this solution (using tf.slice()) as a temporary solution is that you don't need to consider the value of parameter strides.

[dweekly]

Looks like this may fix issue #817

[nealwu]

Thanks! This should be covered by #1063 for 1.0, so I'm going to close.