input: Stop leaking libinput event source on session deactivation

This is easily noticed as a leaked fd on every VC switch.

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Tested-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed