Stil display older image in MvxImageView (iOS) when loading and DefaultImagePath not present

MvxImageView.ImageUrl behavior has difference in iOS and Android.
I consider these as it is better to unite. 

- DefaultImagePath is default value (null)
- Set ImageUrl to MvxImageView
    - Load and display image
-  Change ImageUrl to other image
- Behavior difference between iOS and Android when loading image
    -  Android: Image reseted to empty
    -  iOS: Still display first image

![](http://f.st-hatena.com/images/fotolife/i/iseebi/20140504/20140504050223.gif)
https://github.com/iseebi/MvvmCrossPlayground/tree/master/MvxImageViewBindingSample

I think that it is better to unite operation with Android. Because it use with MvxTableViewCell, display other cell image temporarily when MvxTableView scroll.