Correct android status bar height on android pre-lollipop 
Correct android status bar height on android pre-lollipop 

Due to this change https://github.com/facebook/react-native/pull/6481, no more `SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN` so our custom status view won’t be under the system status any more. The quick fix is just set height of our custom view to `0` on Android Pre-Lollipop
donnguyen/react-native-nav,jineshshah36/react-native-nav