quota delete tenant_id parameter should be required

Makes the quota-delete tenant_id parameter required rather than
optional. Currently if not supplied it will pass 'None' as the tenant id
to the Nova API. It will be silently ignored (at least until
https://review.openstack.org/120971 has merged after which it will fail)
and no quota will be deleted.

Change-Id: I3ad8f36e92ed9ac54bf892f329ce3feb56f01be5
Closes-Bug: 1367127
Merge "quota delete tenant_id parameter should be required"