[#3376] Better fix

- The main point is that we ensure hasItems() internally calls
  internalHasItem(). As such, removing the multiple keys ensures we
  don't have issues with index order of mock objects. Test now passes on
  both 3.7.12 and 3.7.13, on all PHP versions used.
Merge branch 'hotfix/3376'

Backport #3436 to master