Manila cDOT storage service catalog

Like Cinder, Manila has a scheduler that operates (among other things) on extra spec values in share types to determine which backend should receive a new share. In Kilo, Manila will adopt the pools feature from Cinder, such that the scheduler may choose from more than one storage destination per backend. This blueprint will add a number of per-pool attributes to the share stats reported by the cDOT driver to the scheduler, similar to the cDOT driver in Cinder. The added attributes will include high-value storage extra specs, such as deduplication and mirroring, and this work will also add a number of qualified extra specs used by the cDOT driver at share creation time.