As promised in previous commit. Upstream patch:

commit bd0a2609
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date:   Fri Jun 1 19:38:07 2007 +0000

    Make CREATE/DROP/RENAME DATABASE wait a little bit to see if other backends
    will exit before failing because of conflicting DB usage.  Per discussion,
    this seems a good idea to help mask the fact that backend exit takes nonzero
    time.  Remove a couple of thereby-obsoleted sleeps in contrib and PL
    regression test sequences.