To prepare for the unlikely event that Neutron merges and an operator
enables the port-resource-request-groups neutron API extension before
nova adds support for it, this patch rejects server creation if such
extension is enabled in Neutron. Enabling that extension has zero
benefits without nova support hence the harsh but simple rejection.
A subsequent patch will reject server lifecycle operations in a more
sophisticated way and as soon as we support some operations, like
boot, the deployer might rightfully choose to enable the Neutron
extension.
Change-Id: I2c55d9da13a570efbc1c862116cea31aaa6aa02e
blueprint: qos-minimum-guaranteed-packet-rate
e357ad3c23