Recent change Ieffac3732c95846d0e3ec2408a9be4d96e477603 broke the
neutron-k8s py3 tests due to self.private_key being
accessed (_request_certificates method, `if self.private_key`)
before it had been properly set causing an attempt to decode None
Change-Id: I33bbf65e1d170cbc80161c573a381db43468b413