970617 - fix content promotion/deletion of packages and errata

This commit contains a couple of changes to fix the
promotion and deletion of content packages and errata:

- whenever performing a promote/delete of a list of
  packages or errata, 'wait' for the pulp task to complete
  before updating the elastic search index.  If this is not
  done, there is a race condition in which we could update
  the search index before the operation is complete, resulting
  in incorrect data (e.g. repoids)

- when deleting errata, use the 'unit_id' in the request
  to pulp to perform the unassociate; otherwise, the errata
  will not get removed from the repo.
Merge pull request #2425 from bbuckingham/970617

970617 - fix content promotion/deletion of packages and errata