Set [compute]resource_provider_association_refresh=0 to turn off all
periodic refreshing of the provider cache in the report client.
Note that this probably will have zero effect in the nova-next job
other than making sure that that setting doesn't blow up the world.
Because the job is always doing something, there's never a lull long
enough for the refresh timers to expire anyway, so no periodic
refreshing was happening even before this change.
Change-Id: I072b3fa4847db14e5a3f03c775a377e3514224f1