fix deb packaging systemd files

Signed-off-by: Jessica Frazelle <princess@docker.com>
(cherry picked from commit a2ea8f2ad8b93c53253b9c86537dad95e14bd599)

hack/make/.build-deb/rules

@@ -33,6 +33,7 @@ override_dh_installudev:
 	dh_installudev --priority=z80
 
 override_dh_install:
+	dh_install
 	dh_apparmor --profile-name=docker -pdocker-engine
 	dh_apparmor --profile-name=docker-engine -pdocker-engine