On reboot, check the instance volume status on the cinder side.
Verify if volume exists and cinder has an attachment ID, else
delete its BDMS data from nova DB and vice versa.
Updated existing test cases to use CinderFixture while rebooting as
reboot calls get_all_attachments
Implements: blueprint https://blueprints.launchpad.net/nova/+spec/cleanup-dangling-volume-attachments
Closes-Bug: 2019078
Change-Id: Ieb619d4bfe0a6472aefb118b58283d7ad8d24c29