Properly handle accessing instance/class invalid attributes
Properly handle accessing instance/class invalid attributes

At the moment, we assume that if an instance or class attribute was
not found, it is in fact a method.

This patch updates the _Method class, so that when instantiated,
it will attempt to retrieve the method params (as we cache them
anyway). In case this raises a MI_METHOD_NOT_FOUND, we raise
an AttributeError.

alinbalutoiu/PyMI,alinbalutoiu/PyMI,alinbalutoiu/PyMI,cloudbase/PyMI,cloudbase/PyMI,cloudbase/PyMI