Avoid instability in output of new REINDEX SCHEMA test.

The planner seems to like to do this join query as a hash join, making
the output ordering machine-dependent; worse, it's a hash on OIDs, so
that it's a bit astonishing that the result doesn't change from run to
run even on one machine.  Add an ORDER BY to get consistent results.
Per buildfarm.

I also suppressed output from the final DROP SCHEMA CASCADE, to avoid
occasional failures similar to those fixed in commit 81d815dc3ed74a7d.
That hasn't been observed in the buildfarm yet, but it seems likely
to happen in future if we leave it as-is.