plug in the external service registry by default to the aggregator (#4397)
plug in the external service registry by default to the aggregator (#4397)

* plug the external service registry by default

* lint fixes

* lint fix

* lint fix

* lint

Signed-off-by: Shriram Rajagopalan <b02049c3ef4acab83d183f0a320d58683d0c3bb3@vmware.com>

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