Fix small error

While Exim use Spam, we should use Spam instead Junk here too. Otherwise, there will be two folders created: Spam and Junk
Also, directly delete spam instead moving to Junk (and mix with ham messages).

install/ubuntu/roundcube-main.conf

@@ -421,7 +421,7 @@ $rcmail_config['drafts_mbox'] = 'Drafts';
 
 // store spam messages in this mailbox
 // NOTE: Use folder names with namespace prefix (INBOX. on Courier-IMAP)
-$rcmail_config['junk_mbox'] = 'Junk';
+$rcmail_config['junk_mbox'] = 'Spam';
 
 // store sent message is this mailbox
 // leave blank if sent messages should not be stored
@@ -436,7 +436,7 @@ $rcmail_config['trash_mbox'] = 'Trash';
 // display these folders separately in the mailbox list.
 // these folders will also be displayed with localized names
 // NOTE: Use folder names with namespace prefix (INBOX. on Courier-IMAP)
-$rcmail_config['default_folders'] = array('INBOX', 'Drafts', 'Sent', 'Junk', 'Trash');
+$rcmail_config['default_folders'] = array('INBOX', 'Drafts', 'Sent', 'Spam', 'Trash');
 
 // automatically create the above listed default folders on first login
 $rcmail_config['create_default_folders'] = true;
@@ -808,7 +808,7 @@ $rcmail_config['addressbook_search_mods'] = null;  // Example: array('name'=>1,
 $rcmail_config['delete_always'] = false;
 
 // Directly delete messages in Junk instead of moving to Trash
-$rcmail_config['delete_junk'] = false;
+$rcmail_config['delete_junk'] = true;
 
 // Behavior if a received message requests a message delivery notification (read receipt)
 // 0 = ask the user, 1 = send automatically, 2 = ignore (never send or ask)