Close fd on DEVICE_OFF. (LP #276887)

Leaving the fd open means we still get keyboard events after VT switching
away. Coming back, some of these events are replayed on the application that
has the current focus.

Reproduceable:
1. open terminal, focus.
2. VT switch away
3. type something, preferably a password
4. VT switch back, trigger a mouse event
5. Observe the X server guessing your password.

Closing the fd on DEVICE_OFF fixes this. Reopen is handled by the reopen
code introduced with

    commit 9930477cbe
    Author: Peter Hutterer <peter.hutterer@redhat.com>
    Date:   Tue Aug 26 14:33:40 2008 +0930

        Attempt to re-open devices on read errors.

Launchpad Bug 276887
<https://bugs.edge.launchpad.net/ubuntu/+source/xorg-server/+bug/276887>
(cherry picked from commit ccd48d2f50231e2837e0984833641ac79f327ba4)

src/evdev.c

@@ -970,6 +970,8 @@ EvdevProc(DeviceIntPtr device, int what)
                 xf86Msg(X_WARNING, "%s: Release failed (%s)\n", pInfo->name,
                         strerror(errno));
             xf86RemoveEnabledDevice(pInfo);
+            close(pInfo->fd);
+            pInfo->fd = -1;
         }
         if (pEvdev->flags & EVDEV_INITIALIZED)
             EvdevMBEmuFinalize(pInfo);