fix wrong url when clearing cache stats (#3985)
fix wrong url when clearing cache stats (#3985)

* fix wrong url when clearing cache stats

* prefix http:// to pilot_url if the entered url doesn't start with it.

smawson/istio,smawson/istio,geeknoid/istio,istio/istio,istio/istio,smawson/istio,smawson/istio,frankbu/istio,istio/istio,frankbu/istio,geeknoid/istio,frankbu/istio,frankbu/istio,frankbu/istio,smawson/istio,geeknoid/istio,istio/istio,geeknoid/istio,geeknoid/istio,frankbu/istio,istio/istio,geeknoid/istio,smawson/istio