Refactoring: Remove more legacy from release scripts.

- Remove an unused feature that allowed to check for required
  data before each script step.
- Use a relative path to the version file. In the production
  environment, this will point to the cwd/version_file, while
  in the test environment it is fake_cwd/version_file.

TBR=tandrii@chromium.org

Review URL: https://codereview.chromium.org/591783003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24140 ce2b1a6d-e550-0410-aec6-3dcde31c8c00