Close connection after dropping database

If you call any CLI command after DropDatabase in your CLI application it will fail with 
````
[Doctrine\DBAL\DBALException]                                                              
An exception occurred while executing 'SHOW FULL TABLES WHERE Table_type = 'BASE TABLE'':  
                                                                                            
SQLSTATE[3D000]: Invalid catalog name: 1046 No database selected                     
````
Detailed problem description available here: http://blog.nocontext.net/2012/11/symfony-2-drop-create-and-update.html

Also I've created a gist illustrated this issue: https://gist.github.com/iVariable/c9d185f9386fa46249da#file-doctrine_drop_database_fail-php