virtual: Fixed using !INBOX when INBOX wasn't in prefix="" namespace.
virtual: Fixed using !INBOX when INBOX wasn't in prefix="" namespace.

--HG--
branch : HEAD

jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot