Deep copy gateway slice in qualifyGateways func (#4860)
Deep copy gateway slice in qualifyGateways func (#4860)

* Deep copy gateway slice in qualifyGateways func

After https://github.com/knative/serving/pull/4828,
MakeVirtualServices() functions modifies gatewayNames list to
NAMESPACE/GATEWAYFORMAT. Due to this, following logic to find a
particular gateway was broken and Reconcile Gateway stopped working.

To solve it, this patch copy gateway slice in qualifyGateways func.

* Do not copy object but copy in the loop

knative-sandbox/net-istio,knative-sandbox/net-istio