QA: Thanking another users post

For the test on thanking another user's post, we have to assume
    that at least one such post exists. Otherwise the step is marked
    as 'pending' to avoid failure.

    The best practice would be to create a post in the Given clause,
    but since that requires another user account, and it is not part
    of the standard setup (which only has one ENV['mediawiki_user'],
    this approach was not chosen.

Change-Id: I0c67a4f8d44ca04a5e7ab32eff4076a46c3c9752
Merge "QA: Thanking another users post"