Fixes:
Panic: file director.c: line 1175 (director_move_user): assertion failed: (user->host->tag == host->tag)
Panic: file director-request.c: line 303 (director_request_continue_real): assertion failed: (user->host->tag == mail_tag)
{
i_assert(tag_name != NULL);
+ /* If the host already has users, forget all of them. Otherwise state
+ becomes inconsistent, since tag->users won't match
+ user->host->tag. */
+ user_directory_remove_host(host->tag->users, host);
+
host->tag = mail_tag_get(host->list, tag_name);
host->list->vhosts_unsorted = TRUE;
}