libsmbconf:registry: add "state directory" to the list of forbidden parameters

libsmbconf:registry: add "state directory" to the list of forbidden parameters

At the time when the registry configuration was introduced,
the registry database file was placed in the "lock directory".
So the "lock directory" was added to the list of parameters
that may not be changed in the registry configuration
(because the next config reload would then load a different
 registry and drop all the original seetings).

Later, "state directory" and "cache directory" were introduced,
both defaulting to "lock directory". And the registry's location
was changed to "state directory".

It slipped my attention that the forbidden parameters for the
should have been adapted at the time.

So this patch adds "state directory" to the list.
It keeps the lock directory, to catch the case
where the state directory is not explicitly set, hence
defaulting to the "lock directory".

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>