PATCH: user32: close button is not grayed out in shutdown message box

Test Environment:
-Virtual box 3.1.4 r 57640
-Newly downloaded ReactOS 0.3.11 iso (for virtual box)

Steps to reproduce:
1. Start ReactOS with virtual box
2. Click on Start/Turn Off...
3. Click on the X

Expected results:
-Should close the window

Actual results:
-nothing happens