title: Xamarin Auth Store Keychain not working after ios10 upgrade
body: <p>I'm using Xamarin.Auth (<a href="https://components.xamarin.com/view/xamarin.auth/" rel="noreferrer">https://components.xamarin.com/view/xamarin.auth/</a>) to store my credentials, as I've always done.</p>
  
  <pre class="lang-cs prettyprint-override"><code>var accountStore = AccountStore.Create ();
  foreach (var account in  accountStore.FindAccountsForService("myAppName"))
      accountStore.Delete (account, "myAppName");
  
  AccountStore.Create().Save(acc, "myAppName");
  </code></pre>
  
  <p>After the upgrade to iOS 10 I get this error storing credentials:</p>
  
  <pre><code>"Could not save account to KeyChain: -34018"
  
  at Xamarin.Auth.KeyChainAccountStore.Save (Xamarin.Auth.Account account,System.String serviceId) [0x000b2] in &lt;402cf9b3716845b3bdddef581cb33a3e&gt;:0 
  </code></pre>
  
  <p>Latest version installed 1.2.3.1
  The problem seems to persist only on the SIMULATOR</p>