The maximum amount of shared (deduplicated, cloned) data on
a Data ONTAP FlexVol (i.e. a Cinder pool) is 640TB. The only thing
more surprising about that number is that we have customers hitting
it. The symptom is that operations such as cloning Cinder volumes
fail because no more blocks may be shared. The fix is to report the
level of consumption to the scheduler for optional incorporation
into the filter & goodness functions, so that pools nearing the shared
block limit may be shielded from further provisioning requests.
Implements: blueprint netapp-cdot-report-shared-blocks-exhaustion
Change-Id: I01b7322f7ddb05ee5e28bcb1121a90a6ea307720
