IPMI driver sets bootdev option persistently.

This patch changes baremetal ipmi driver's behavior with regards to
setting the chassis boot device.

Previous behavior: set bootdev = pxe for next boot only.
New behavior: set bootdev = pxe persistently.

Fixes bug 1178092

Change-Id: I735965422a950fbd249414b5eecd0a1b21dbabea
Merge "IPMI driver sets bootdev option persistently."