criu: systemd: allow enabling criu service

Currently it is not possible to enable criu service after "make install",
as it has no [Install] section in criu.service file.
Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

scripts/sd/criu.service

@@ -3,3 +3,6 @@ Description=Checkpoint Restore in Userspace daemon
 
 [Service]
 ExecStart=/usr/sbin/criu service -o /var/log/criu-service.log
+
+[Install]
+WantedBy=multi-user.target