Fix node to chassis and port to node association

This patch is fixing the Ironic API to allow "replace" (or "add" that
acts like a replace on an existing field) the chassis_uuid field from
nodes and the node_uuid field from ports.

Closes-Bug: #1340196
Change-Id: I89533bcd2e4ab0b1d453c4d9424e573b23703827
Merge "Fix node to chassis and port to node association"