Use Postgres adapter method for dropdb and createdb in the jdbc adapter so we get username,password,host and port settings

Currently if you use JRuby and connect to a postgres database it will not use the database host,port,username or password settings in database.yml when it drops or creates a database.  The postrges adapter does use all of these settings.  This change changes the jdbc adapter to use the postgres adabter's implementation to drop and create a database.