Store tenant_id from keystone and use for quotas

Some calls in nova require a tenant_id when it could be interpreted
from the current authentication data, so save the tenant id and
use it in the quotas command if tenant_id is not specified.

Change-Id: I89647cfe9da73bc474ef80a61a5678db42a5571c
Merge "Store tenant_id from keystone and use for quotas"