Automatic merge from submit-queue

selector: make sure value of GT and LT is integer

GT and LT in selector has been introduced in Node Affinity feature: https://github.com/kubernetes/kubernetes/pull/19758, https://github.com/kubernetes/kubernetes/pull/18261

According to the API:

>  If the operator is Gt or Lt, the values array must have a single element, which will be interpreted as an integer.

But the implementation has parsed it as float64:
https://github.com/kubernetes/kubernetes/blob/ef0c9f0c5b8efbba948a0be2c98d9d2e32e0b68c/pkg/labels/selector.go#L183

Modeling integer as float is dangerous. We don't even have fixed precision guarantee when doing comparison.

This PR is to get rid of this pre-optimization and convert **integer** to int64.