no gerrit-git-prep jobs should use git scm module

Any job that uses gerrit-git-prep should absolutely not use the git scm module. To do otherwise causes jenkins to do too much work, significantly slowing job execution, as well as possibly putting a significant load on the gerrit server.

Any job that uses the git scm module needs to have its workspace wiped out _after_ the git scm module is removed from the job config.

This has all been done once already, but the jenkins job filler undid all of that work.