modified Makefile to:
- stop service before install when updating reported at http://forum.lede-project.org/t/ddns-scripts-upgrade-issue/456/1
- run uci-defaults for all packages
- modify services files only on new installation
still some commands already covered by default_postinst() etc. but they are in there for backward compatibilty.

Signed-off-by: Christian Schoenebeck <christian.schoenebeck@gmail.com>