Fix hardcoded default all-context-access policy for middleboxes, improve...

Fix hardcoded default all-context-access policy for middleboxes, improve container status management

- Middlebox context access will now match that configured by the
  client and server

- The container access APIs now provide error results when trying to
  perform an access on a container for which the middlebox does not
  have the required rights

- There are new API points for querying container status