deblayout: Add missing close tags for <div id="content"> and messages

The #content div must be closed before the #footer div is opened. For
the messages, there is an opening <div>, but a closing </li>. I assume
that the </li> should be a </div>, as there is no <ul> or <ol> around
the list.

Signed-off-by: Julian Andres Klode <jak@debian.org>