Implement thin provisioning support for E-Series

Implement thin provisioning support for E-Series

Implement a new extra spec, 'netapp_thin_provisioned', that will allow
users to define thin provisioned Cinder volumes on E-Series storage,
alongside pre-existing extra specs such as
'netapp_eseries_data_assurance', 'netapp_eseries_flash_reach_cache',
'netapp_raid_type', etc.

We have a followup patch, https://review.openstack.org/#/c/215801/ ,
that reports 'thin_provisioning_support=True/False' and same for
'thick_provisioning_support', in accord with the scheduler-based
over-subscription support added in Kilo.

We are not yet attempting to implement the get_capabilities()
feature just merged into Liberty
(https://review.openstack.org/#/c/201243/)
but fully intend to do so in a way that conforms with that plan of
record.

Partially-Implements: blueprint netapp-eseries-additional-extra-specs
DocImpact
Change-Id: Ia00b56e6d6a644cff81791bbd04e97f0c02b9e65