quota testcases use tenant_name should use tenant_id

Test case related to quota usage (test_show_quota_usage,
test_cinder_quota_defaults and test_cinder_quota_show)
uses tenant name, ideally it should use tenant id as quota
requires UUID of tenant and not tenant name.

Cinder quota-show ideally requires tenant_id to show quota.
As there is bug in cinder (BUG: 1307475) , that if we give
non-existent tenant_id still cinder show the quota and
returns 200 (OK). Hence, these testcases should use
tenant_id and not tenant_name.

Change-Id: Icab25afd482b34290bc74be2ba420f6b016dde18
Closes-Bug: #1321617
Merge "quota testcases use tenant_name should use tenant_id"