By design, Ironic will be making hardlinks from /var/lib/ironic/master_images
into /httpboot. On a machine where /var is on a separate partition, deployment
will succeed but operation will fail with some errors like:
OSError: [Errno 18] Invalid cross-device link
in ironic conductor logs. This patch adds an extra configuration
variable which allows the user to configure the path location
properly and to overcome this issue.
Change-Id: If90b49c75ff1a224d8d539036b89c1c7ee030bd0