Extend default resource loading in live cluster to istio resources

[tanyaveksler]

Currently there are the following possible combinations for handling resources in live cluster:

• nca -r k8s -r istio => loads both k8s and istio reources
• nca -r k8s => loads only k8s resources
• no -r given => loads only k8s resources

We should probably change the default assumption that both k8s and istio resources are handled in live cluster.
What do you think, @zivnevo ?

[tanyaveksler]

We decided to remove the default (running without -r flag), and to give a warning in this case.