Automatic SignOut in OpenERP 7 during System Shutdown
Can we make it in such way that when we Shutdown the System it should
  SignOut Automatically without the User interference

there is no need to logoff the users. HTTP is a transactional protocol. All is done when the client has made any request. After any client request the system is always in a clean state. There is no state in the clients, that must be flushed to the server before switching off.
When you shutdown and start-up the OpenERP server again, all clients has lost their "session" and if they do a new request they will be redirect to the login page. 
Of course, this could by annoying when users starts to fill a screen form (still in browser), send the request and then get redirected to the login, because there were no valid session.
To SignIn/SignOut into OpenERP 7 we have to login into OpenERP and click on the Icon which is on the right top just beside the "Compose New Message" Icon. Now most of the users forget to  SignOut from ERP. Can we make it in such way that when we Shutdown the System it should SignOut Automatically without the User interference. Just like a Windows service. Is there any way to do that ?
Please help me out.