Neutron provides an API to retrieve default quotas since newton.
Unfortunately there is no corresponding neutron API extension
is not defined, so there is no way to detect it via API.
The API exists since newton, so this commit just switches to
the default quota API.
Closes-Bug: #1337473
blueprint make-quotas-great-again
Change-Id: Ia826b67f4cec7d95335c62ef98c3040feaa06117