dropdb - still occasional failures

We still seem to have occasional problems with dropdb while running
contrib installcheck. The symptoms look like this:

============== dropping database "regression" ==============
dropdb: database removal failed: ERROR: database "regression" is being accessed by other users
============== creating database "regression" ==============
createdb: database creation failed: ERROR: database "regression" already exists
pg_regress: createdb failed

Example: (FBSD again)
http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=cockatoo&dt=2004-12-13%2008:10:01

I guess we could put a small sleep before dropdb in pg_regress.sh to
make sure a backend from a previous client had enough time to clean up
after itself, but I am wondering if this is a symptom of a larger problem?

cheers

andrew