server/xi2: use the DeviceInterface for the evemu device
server/xi2: use the DeviceInterface for the evemu device

Plus, that also fixes the device path that got busted when I imported these
tests from the xserver integration-testing branch

Signed-off-by: Peter Hutterer <b9c50af7afa7642f6f854434cda9ffe54ece8b85@who-t.net>

freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests,freedesktop-unofficial-mirror/xorg__test__xorg-integration-tests