Accessibility window query APIs should respect root name space.

1. The window query API used to not-respect the root name space
   while traversing the parent relation i.e. a client was able
   to fetch the parent of a root name space node.

2. Children that are root name space were reported but their descendants
   not. Actually such children should not be reported since they are
   the root of a separate logical sub-tree. Such a tree is exposed by
   its root allowing its traversal. The accessibility APIs should be
   able to explore a virtual tree, i.e. one with a descendant which is
   root name space, only if an accessibility event from there was received.

bug:5480096

Change-Id: I4c4d805aa2f6d4edba86eda213b5239bea83eed2