[A]Resolve issue where calling Focus in an unfocus event would fail

 [A]Resolve issue where calling Focus in an unfocus event would fail

Fixes https://bugzilla.xamarin.com/show_bug.cgi?id=39702 without API change. This does cause android to always indicate a focus event was succesful now because we have no way of knowing ahead of time if it will succeed or fail. That said we always already indicated that unfocus was successful because android has no way of reporting such a failure.