Fix build failures

For some reason changing `.find` to `.unscoped.find` in
https://github.com/rails/rails/commit/f766abd4cf3eb75469d3646cfb6d85e668c619f3
caused `scoping` to leak in some tests when run in isolation (looks like
a concurrency issue?). `relation_scoping_test.rb` is a case that failed.
From what I can tell it should not be possible, but changing to the
block form fixes it. There is a deeper issue that I can't seem to find.
/cc @senny