CDVViewController: Fix KeyboardShrinksView on iOS 7

I was updating my App to iOS 7 and Cordova 3.0.0 when I noticed that KeyboardShrinksView does not properly reset the WebView when hiding the keyboard. I have a tab bar positioned absolutely (left: 0, right: 0, bottom: 0) and it didn't show up again after hiding the keyboard.

I did not use KeyboardShrinksView on iOS 6 or with any prior Cordova Version so I don't know if this problem already existed before.

Please let me know if I need to make any changes to this pull requests - preliminary tests show this works fine for me!