Comment 4 for bug 1348166

Reviewed: https://review.openstack.org/109293
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=3f19a97e4f250c49742655ef94edd6e33cc9845a
Submitter: Jenkins
Branch: stable/5.0

commit 3f19a97e4f250c49742655ef94edd6e33cc9845a
Author: Evgeniy L <email address hidden>
Date: Thu Jul 24 17:03:28 2014 +0400

    Upgrades, fix rollback for bootstrap engine

    * changed rollback strategy for bootstrap
      upgrade engine, in previous strategy we
      made symlink from previous version of
      bootstrap to /var/www/nailgun/bootstrap
      it doesn't work because in 5.0 version
      cobbler container mounts /var/www/nailgun
      directory as /repo, as result symlinks
      which we make on the host system are
      broken inside of container.

      Instead of symlink command we rename
      previous version to /var/www/nailgun/bootstrap

    * use lexists instead of exists because
      exists returns False on broken symlinks

    * fixed docker engine rollback, there
      was wrong definition of previous version
      of fuel

    Change-Id: Id0b50835410e005fde76f421981b4616211ddcbf
    Closes-bug: #1348166