inst_upgrade_urls.rb client fixes

- remove old repositories (repo files) to avoid loading old
  SLE11 repositories when refreshing a registered service
  (bnc#880971)

- remove old services to get rid of the old NCC service

(Note: everything is backed up into /var/adm/backup/upgrade/zypp
directory)

- 3.1.88
code review fixes

better find the repository *.repo file
Merge pull request #208 from yast/remove_old_repos_and_services

inst_upgrade_urls.rb client fixes