This commit implements the ability for an admin to manage
existing RSD composed nodes with Valence. In the event that
an RSD pod manager contains composed nodes that were created
without Valence, it's possible to use this function to
add those nodes to the Valence database.
Change-Id: I13e8076fb718ebd356cb7b4839cfb4b83c798672
Implements-blueprint: manage-node
5ce2d68ed7