Update comment and mock about autospec not working on staticmethods
Update comment and mock about autospec not working on staticmethods

Update the comment where autospec was not used. And use spec_set.

When using a mock, 'autospec=True' doesn't work on staticmethods
(https://bugs.python.org/issue23078). For those cases, use
spec_set=types.FunctionType.

Change-Id: Ib6e7f820eb7ba402e1e62656d6b18e49aa4b00ef

openstack/ironic,openstack/ironic