Add neutron quotas management in benchmark context

This patch allows to modify quotas related to neutron for
generated benchmark's tenants by extended the context object,
allowing to run large scale scenarios.

Also correct some copy/paste error in cinder/nova quotas tests.

Blueprint benchmark-context-tenant-quotas

Change-Id: Ib588e6fdf8cdd5c81cefaa4555c437cfaf92fad7
Merge "Add neutron quotas management in benchmark context"