(PUP-1843) Clean up hiera terminus

The data_binding/hiera_spec.rb had a specific after block to clear up
the hiera terminus for following tests.  Moved this to the
shared_behaviors/hiera_indirections so that both indirector/hiera_spec
and data_binding/hiera_spec would be cleaned up, preventing order
dependent errors caused by global terminus state leaking between tests.