Fix directory website redirection

When a URL referred to a directory, the webserver is meant to redirect
to one with a trailing slash.  However it was returning a relative
path, so, for example, https://sel4.org/Foundation/Summit redirected
to https://sel4.org/Foundation/Summit/Foundation/summit/

Make it an absolute path.

Signed-off-by: Peter Chubb <[email protected]>

examples/webserver/webserver.py

@@ -127,7 +127,7 @@ async def try_suffices(path, suffices):
         # exists, and we did not find any files with the name suffixed
         # by a standard extension, so redirect the client to the form
         # with appropriate trailing slash.
-        return 301, f'{relative_path}/', None
+        return 301, f'/{relative_path}/', None
 
     return 404, None, None