Fix `NoopQuotaDriver.get_(project|user)_quotas` format

The quota API extension expects `get_project_quotas` and `get_user_quotas` to
return a dictionary where the value is another dictionary with a `limit` key.

The `DbQuotaDriver` adhered to this spec, but the `NoopQuotaDriver` didn't.

This fixes the `NoopQuotaDriver` to return the results in the correct format.

Fixes bug 1244842

Change-Id: Iea274dab1c3f10c3cb0a2815f431e15b4d4934b1
(cherry picked from commit 711a12b4029cd1544d26d147d8a67e110e056124)
Merge "Fix `NoopQuotaDriver.get_(project|user)_quotas` format" into stable/havana