set result after cleanup of locationmanager xamarin#1489

On IOS if you like to request LocationAlways you have to request locationWhenInUse first. This means in an average implementation one would have to consecutive call
await Permissions.RequestAsync<Permissions.LocationWhenInUse>();  
Permissions.RequestAsync<Permissions.LocationAlways>();  
Both use the static LocationManager instance.
Since RequestAsync<Permissions.LocationWhenInUse>() sets the result of the task completition source before cleaning up its locationManager there is a race condition where RequestAsync<Permission.LocationAlways>() already runs and thus this cleanup disposes the locationManager used by the second call. This will not always be the case but in my test around 50% of the time. Workaround wait 3-10 seconds in between the calls

Xamarin.Essentials/Permissions/Permissions.ios.tvos.watchos.cs

@@ -186,9 +186,9 @@ void LocationAuthCallback(object sender, CLAuthorizationChangedEventArgs e)
                         }
 
                         del.AuthorizationStatusChanged -= LocationAuthCallback;
-                        tcs.TrySetResult(GetLocationStatus(whenInUse));
                         locationManager?.Dispose();
                         locationManager = null;
+                        tcs.TrySetResult(GetLocationStatus(whenInUse));
                     }
                     catch (Exception ex)
                     {