nova will throw an error if you attempt to add a node to a host
aggergate that does not "exist" in terms of nova. Therefore
depending on the order in which your nodes come up, you can have puppet
attempting to add a node to a host aggregate when the node does not yet
have nova compute installed and "registered". This is especially true if
you manage your host list with a hiera list or other mechanism that is
not directly tied to nova-compute being installed. Instead of blowing up
with an error, we will instead print a warning and let eventual
consistency solve it as your nodes are installed.
Since it is inefficient to call nova host-list once for every member of
a host aggregate we also cache this information and similarly cache the
output of nova aggegrate-details which previously was also called
once for every member of every aggegrate.
Change-Id: I6249cd070ad804c626d880decb6767e2ff14dcbd
580f6289d9