MODE-1865 Correct behavior of joins when using 'LIMIT 1'

Do not push down isExists query hints to join QueryContexts. Doing so will cause joins to bail immediately when either side yields one row whereas in a JOIN you are looking for find rows that satisfy the join (and not just checking the first row from either side).

This pull-request adds a single commit to the three commits in an [earlier pull-request](https://github.com/ModeShape/modeshape/pull/757).