Second authentication attempt on Android causes exception

[VitalyKnyazev]

An attempt was made to transition a task to a final state when it had already completed:

1. TaskCompletionSource`1[TResult].SetResult (TResult result)
2. AndroidWebAuthenticationUi+<>c__DisplayClass11_0.<AuthenticateAsync>b__0 (System.Object s, Microsoft.OneDrive.Sdk.Authentication.AuthCompletedEventArgs e)
3. AndroidWebAuthenticationActivity.OnPageFinished (Android.Webkit.WebView view, System.String url)
4. AndroidWebAuthenticationActivity+Client.OnPageFinished (Android.Webkit.WebView view, System.String url)
5. WebViewClient.n_OnPageFinished_Landroid_webkit_WebView_Ljava_lang_String_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_view, System.IntPtr native_url)
6. (wrapper dynamic-method) System.Object:affcf147-32b1-4f41-9270-f8e2881c04f3 (intptr,intptr,intptr,intptr)