elput: Fix multiple open/close of drm devices

elput: Fix multiple open/close of drm devices

When I added the code to probe drm devices to ensure they're
modeset capable (ref 414d406b3b442216543cdaef112787696ae09898)
I didn't realize elput didn't allow us to open and close more than
one drm device at startup without blowing up libinput.

This is a somewhat dirty hack to rough that in.

The problem is that open/close the device during startup will
result in an async "gone" callback from logind, which then kicks
off an input shutdown.  We need to try harder to only do that
shutdown when it makes sense.