Netapp drivers support for pool-aware scheduling

Adds pools support for all NetApp drivers: eseries, 7mode (iscsi and nfs), and
cmode (iscsi and nfs). With 7mode and cmode drivers, a pool is one-to-one with a
Ontap flexvol. With eseries, a pool is one-to-one with a dynamic disk pool.

DocImpact
Implements: blueprint pool-aware-cinder-scheduler-support-in-netapp-drivers

Change-Id: Ie6f155df7bc1ae2cd5f7fa39f1b1a0ad38075988
Merge "Netapp drivers support for pool-aware scheduling"