Make dest NATIVE_URI compatible with source CAMERA

When using the camera in iOS, UIImagePickerControllerReferenceURL does not exist because the image only exists in memory immediately after taking a photo. This waits for the image to be written to disk before firing the JS callback when Camera.SourceType.CAMERA, Camera.DestinationType.NATIVE_URI, and saveToPhotoAlbum=true are used together in iOS.