Create directives model before importing OVAL Directives into it.
Create directives model before importing OVAL Directives into it.

I forgot to add the line which creates a directives model when I introduced the
OVAL Session. The line was forgotten during the refactoring and wasn't caught
yet because we don't have and UNIT tests using OVAL Directives.

jan-cerny/openscap,redhatrises/openscap,jan-cerny/openscap,openprivacy/openscap,jan-cerny/openscap,Hexadorsimal/openscap,redhatrises/openscap,openprivacy/openscap,openprivacy/openscap,OpenSCAP/openscap,Hexadorsimal/openscap,redhatrises/openscap,ybznek/openscap,mpreisler/openscap,ybznek/openscap,OpenSCAP/openscap,OpenSCAP/openscap,redhatrises/openscap,ybznek/openscap,ybznek/openscap,openprivacy/openscap,mpreisler/openscap,jan-cerny/openscap,openprivacy/openscap,Hexadorsimal/openscap,ybznek/openscap,jan-cerny/openscap,Hexadorsimal/openscap,mpreisler/openscap,OpenSCAP/openscap,mpreisler/openscap,Hexadorsimal/openscap,mpreisler/openscap,mpreisler/openscap,ybznek/openscap,jan-cerny/openscap,OpenSCAP/openscap,redhatrises/openscap,OpenSCAP/openscap,redhatrises/openscap,openprivacy/openscap,Hexadorsimal/openscap