fix hang-up behaviour (#702)

Author: kanat

dogfooding/lib/screens/call_screen.dart

@@ -134,6 +134,10 @@ class _CallScreenState extends State<CallScreen> {
         body: StreamCallContainer(
           call: widget.call,
           callConnectOptions: widget.connectOptions,
+          onCancelCallTap: () async {
+            await widget.call.reject();
+            await widget.call.leave();
+          },
           callContentBuilder: (
             BuildContext context,
             Call call,

dogfooding/lib/screens/home_screen.dart

@@ -41,7 +41,8 @@ class _HomeScreenState extends State<HomeScreen> {
       onButtonClick: (call, type, serviceType) async {
         switch (serviceType) {
           case ServiceType.call:
-            call.end();
+            call.reject();
+            call.leave();
           case ServiceType.screenSharing:
             StreamVideoFlutterBackground.stopService(ServiceType.screenSharing);
             call.setScreenShareEnabled(enabled: false);