Reduce delay for failover test attempts

Should manually calculating gateway IP really resolve the issue with
false-positive failover tests, the delay shouldn't be necessary at all.

Reference: a168841
Signed-off-by: Simon Rozman <simon@rozman.si>

eduVPN/ViewModels/VPN/Session.cs

@@ -434,7 +434,7 @@ public Session(ConnectWizard wizard, Server server, Configuration config, Expira
                 var gateway = new IPAddress(gatewayBytes).ToString();
                 for (; ; )
                 {
-                    if (SessionAndWindowInProgress.Token.WaitHandle.WaitOne(1000))
+                    if (SessionAndWindowInProgress.Token.WaitHandle.WaitOne(250))
                         return;
                     foreach (var iface in NetworkInterface.GetAllNetworkInterfaces()
                         .Where(n =>