Install D-Bus policy in /usr instead of /etc (Closes: #1041237)
SDDM installs its D-Bus policy file in /etc/dbus-1
.
Since Debian 9 the standard directory for package-installed
D-Bus policies is /usr/share/dbus-1
.
See: https://bugs.debian.org/1006631
Fixes: lintian: dbus-policy-in-etc