Merge pull request rails-sqlserver#700 from amatsuda/set_single_user_before_drop

SET SINGLE_USER before dropping the database

Author: wpolicarpo

lib/active_record/connection_adapters/sqlserver/database_tasks.rb

@@ -12,6 +12,7 @@ def create_database(database, options = {})
 
         def drop_database(database)
           name = SQLServer::Utils.extract_identifiers(database)
+          do_execute "ALTER DATABASE #{name} SET SINGLE_USER WITH ROLLBACK IMMEDIATE"
           do_execute "DROP DATABASE #{name}"
         end