Adds a new node field "manage_boot" to store this value. When it is set
to False, neither boot device nor power state are touched for this node.
Instead, we expect a 3rd party to handle them.
We still manage the PXE filter because the node may need DHCP.
Change-Id: Id3585bd32138a069dfcfc0ab04ee4f5f10f0a5ea
Story: #1528920
Task: #11338