Remove use of "quota_tenant_usages" in Volumes page

Replace it instead with a direct call to the Cinder limits. The
generic usage quotas method performs some operations that can be
costly when there is a large number of volumes.

Change-Id: Ib5601d34a1854f4b190b3bc106504f384561fc30
Partial-Bug: #1334608
Terminate Instance button doesn't work

Bug associated with Bootstrap 3 upgrade:
https://review.openstack.org/#/c/107042/ >
openstack_dashboard/dashboards/project/instances/tables.py
the addition of the "ajax-modal" css class to TerminateInstance is
causing the problems. We did not have this class before.

Change-Id: I30e28120d9766ada56a9d179ed7ac17f8b2ad6e5
Closes-Bug: #1349608
Merge "Terminate Instance button doesn't work"
Merge "Remove use of "quota_tenant_usages" in Volumes page"