when user opens the firewall or any of its children objects in the
editor. This includes any rule set, interface or any other child
object.
Also moved function Interface::getParentHost() from class Interface to
class Host as static FWObject* Host::getParentHost(FWObject *o). Its
behavior is now more logical, it returns non-NULL pointer only if an
object actually has a parent that is host, firewall or cluster. Old
function Interface::getParentHost() returned non-NULL pointer even
when object was not in the proper position in the tree.
Now this function can be used to get parent host/firewall/cluster for
any child object rather than only interface.
I had to fix bunch of problems in unit tests that got uncovered because
new function behaves in a more strict way (returns NULL when there is
no parent of correct type).
