base-files: supress service restart of umount

Restart is in default implemented so it calls stop and start. This is
pretty unsafe to call on umount service. This service should not do
anything on restart the same way as on start. Only use of this service
is on stop.

Signed-off-by: Karel Kočí <cynerd@email.cz>
(cherry picked from commit 537b801c54)

package/base-files/files/etc/init.d/umount

@@ -2,6 +2,11 @@
 # Copyright (C) 2006 OpenWrt.org
 
 STOP=90
+
+restart() {
+	:
+}
+
 stop() {
 	sync
 	/bin/umount -a -d -r