Fix guest icon is not clickable after adding user

When addUser icon is clicked, it becomes disabled to prevent double clicking.
And this icon is newer enabled again in case of successfull user creation.
When user is added, icon for New user is added to recycler view before guest icon.
So, when user selection is opened again guest icon is not clickable, because it is disabled.

Enabling addUser button after successfull user creation fixes this issue.

Test: - Set pin: adb shell locksettings set-pin 0000
- Lock board: adb shell input keyevent KEYCODE_POWER
- Wake up: adb shell input keyevent KEYCODE_POWER
- Click cancel button
- Click "Add User" -> Click Ok
- Set pin
- Lock board
- Wake up
- Click cancel button
- Click guest button

Bug: 170382676
Signed-off-by: Artem Radchenko <artem.radchenko@globallogic.com>
Change-Id: Ie9f3e9b765123207d1217ae2434608c3316923f4
Signed-off-by: Akash Srivastava <akashniki@gmail.com>

Author: Artem Radchenko

packages/CarSystemUI/src/com/android/systemui/car/userswitcher/UserGridRecyclerView.java

@@ -567,6 +567,9 @@ protected void onPostExecute(UserInfo user) {
                         Log.e(TAG, "Failed to switch to new user: " + user.id);
                     }
                 }
+                if (mAddUserView != null) {
+                    mAddUserView.setEnabled(true);
+                }
             }
         }