Previous 'state' variable set variants do not know and use metadata. The
'direct' storage backend's read function honors this, but not its
counterpart the write function. This makes an update of the 'state'
variable set impossible.
This change makes backward compatibility explicit, else it complains in
the read function as well. With some more debug output it helps the
developer to do things right.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>