psql: Don't try to print a partition constraint we didn't fetch.

psql: Don't try to print a partition constraint we didn't fetch.

If \d rather than \d+ is used, then verbose is false and we don't ask
the server for the partition constraint; so we shouldn't print it in
that case either.

Maksim Milyutin, per a report from Jesper Pedersen.  Reviewed by
Jesper Pedersen and Amit Langote.

Discussion: http://postgr.es/m/2af5fc4d-7bcc-daa8-4fe6-86274bea363c@redhat.com