specifying -D database_prefix works when same as dirname
specifying -D database_prefix works when same as dirname

Previously if the application directory name was the same
as the name specified as the database prefix in a parameter
when running config/setup.rb the theme name would instead
be used for the database_prefix.
concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse,concord-consortium/rigse