property: return EXIT_FAILURE if at least one device fails (#90226)

list-props allows for multiple devices to be queried simultaneously, so we
don't break out of the loop but rather change the exit code if at least one of
the devices doesn't exist.

X.Org Bug 90226 <http://bugs.freedesktop.org/show_bug.cgi?id=90226>

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