nova-network quotas are considered in usage/quotas.py previously.
This commit completely always disables nova-network quotas.
The nova API wrapper ensures nova-network quota fileds are not
included in responses from tenant_quota_get and default_quota_get.
Drop nova-network quota fields from the Admin Defaults panel and
the Identity Project quota form.
blueprint make-quotas-great-again
Change-Id: Ie69d3003f62d3a124d79a1fea003092f73372187