Remove legacy context API usage
Remove legacy context API usage

Summary:
Changelog:
[General][Removed] - Remove legacy context API usage in AppContainer

Reviewed By: kacieb

Differential Revision: D27681097

fbshipit-source-id: 7391be577955171ade5b8fd53cf274900f88e7ca

pandiaraj44/react-native,janicduplessis/react-native,arthuralee/react-native,myntra/react-native,myntra/react-native,facebook/react-native,janicduplessis/react-native,facebook/react-native,arthuralee/react-native,arthuralee/react-native,facebook/react-native,janicduplessis/react-native,myntra/react-native,myntra/react-native,javache/react-native,javache/react-native,myntra/react-native,janicduplessis/react-native,javache/react-native,javache/react-native,pandiaraj44/react-native,pandiaraj44/react-native,javache/react-native,janicduplessis/react-native,facebook/react-native,myntra/react-native,myntra/react-native,myntra/react-native,pandiaraj44/react-native,pandiaraj44/react-native,janicduplessis/react-native,javache/react-native,myntra/react-native,pandiaraj44/react-native,javache/react-native,facebook/react-native,javache/react-native,javache/react-native,arthuralee/react-native,pandiaraj44/react-native,pandiaraj44/react-native,janicduplessis/react-native,janicduplessis/react-native,facebook/react-native,facebook/react-native,arthuralee/react-native,facebook/react-native,facebook/react-native