BaremetalProvisionStates.NOSTATE (``None``) was replaced by AVAILABLE
("available") in Ironic version 1.2. ENROLL ("enroll") state was introduced
in version 1.12. This patch also updates the
BaremetalScenarioTest.terminate_instance method to wait for etiher NOSTATE
or AVAILABLE.
Change-Id: I067504e49f68929298c91e61819aa9a61169fe52