Minor fixes to rebuild_base_installers_for_seattlegeni.sh.

* The SOFTWARE_UPDATE_URL was updated.
* The user was made configurable.
Update rebuild_base_installers_for_seattlegeni.sh
Update rebuild_base_installers_for_seattlegeni.sh
Merge branch 'v2' of https://github.com/aot221/dist into git-aware-buildscripts