DS8K driver needs two new properties in extra-specs, so that user
can specify pool or lss or both of them to allocate volume in their
expected area.
On the other hand, driver needs to verify the pool and lss user
set to avoid they set wrong pool or lss.
DocImpact
Implements: blueprint specify-pool-lss
Change-Id: Ibd98fa3246118aa6ad5d86ecbfe46ae78de87716
