Fix order of calls on Picker
Fix order of calls on Picker

Summary:
In previous implementation, `setNativeProps` was called before `render`. These two methods can change value of `selectedIndex` and it matters in which order they arrive in native.

This was fine in Paper because 1st selectedIndex is set from `setNativeProps` with wrong value and then correct value comes from props.

However in Fabric, 1st selectedIndex comes from props (this is the correct one), and 2nd comes from command which has the incorrect value.

changelog: [internal]

Reviewed By: TheSavior

Differential Revision: D18240118

fbshipit-source-id: dca897306d3e858b9175b2f81356c76f5a0f79e2

facebook/react-native,exponent/react-native,facebook/react-native,hammerandchisel/react-native,javache/react-native,myntra/react-native,exponent/react-native,janicduplessis/react-native,javache/react-native,janicduplessis/react-native,facebook/react-native,exponentjs/react-native,pandiaraj44/react-native,hammerandchisel/react-native,exponentjs/react-native,javache/react-native,facebook/react-native,pandiaraj44/react-native,myntra/react-native,exponent/react-native,janicduplessis/react-native,myntra/react-native,javache/react-native,pandiaraj44/react-native,hoangpham95/react-native,javache/react-native,facebook/react-native,pandiaraj44/react-native,pandiaraj44/react-native,hoangpham95/react-native,exponentjs/react-native,javache/react-native,exponentjs/react-native,facebook/react-native,janicduplessis/react-native,hammerandchisel/react-native,myntra/react-native,hoangpham95/react-native,exponentjs/react-native,facebook/react-native,pandiaraj44/react-native,pandiaraj44/react-native,exponentjs/react-native,arthuralee/react-native,exponent/react-native,exponent/react-native,hammerandchisel/react-native,hoangpham95/react-native,janicduplessis/react-native,myntra/react-native,hoangpham95/react-native,hammerandchisel/react-native,arthuralee/react-native,hammerandchisel/react-native,arthuralee/react-native,janicduplessis/react-native,exponent/react-native,hoangpham95/react-native,arthuralee/react-native,pandiaraj44/react-native,exponentjs/react-native,myntra/react-native,hoangpham95/react-native,myntra/react-native,janicduplessis/react-native,exponent/react-native,facebook/react-native,myntra/react-native,janicduplessis/react-native,hoangpham95/react-native,exponentjs/react-native,facebook/react-native,javache/react-native,exponent/react-native,javache/react-native,myntra/react-native,javache/react-native,hammerandchisel/react-native,hammerandchisel/react-native,arthuralee/react-native