RubyOnRails build 8927.1 fixed

The build has been fixed.

CHANGES

This change of CI build status is a result of fixing the build
environment according to
http://cruisecontrolrb.thoughtworks.com/builds/RubyOnRails/8906.

rake test_postgres now accesses the test database with the username of
the shell account running the tests (until [8906], it was hard-coded
as 'postgres').