This patch adds the missing destruction of session-state objects of
local services when closing a session. Because of the missing
destruction, those session-state object remained part of the server
ID space. This becomes a problem once the backing store of the session
state object vanishes, that is when the client child gets removed from
the sandbox. Hence, the removal of a child with an open session to a
local service would lead to the corruption of the server ID space.
This patch adds the missing session.destroy() call.
Fixes#4044