fixed possibleinferiors.py so it matches windows behaviour

fixed possibleinferiors.py so it matches windows behaviour

This test code builds the possibleInferiors for every class in the
schema on a target machine, and compares it to the servers
possibleInferiors attribute.

The MS-ADTS spec describes how to calculate possibleInferiors for a
object, but it seems to have some bugs. The spec says that we need to
use AUXCLASSES, and it does not mention the use of the SUBCLASS
tree. In trying to match windows behaviour, I found that I needed to
ignore the AUXCLASSES and build a SUBCLASSES tree.