Hanging NSM interfaces inside target pods

[KatrinSalt]

The following issue has been noticed while running multi-stream test:

Periodically, nsm- interfaces are not wiped out from the list of interfaces after the target pod is disconnected from the stream-n.

The multi-stream test goes as follows:

1. Deploy conduit-b/stream-b/flow-b
2. Connect each target pod to stream-b and afterwards test traffic through conduit-a/stream-a
3. Install stream-a-2 in conduit-a
4. Connect each target pod to stream-a-2 and afterwards test traffic through conduit-a/stream-a
5. Close connection to stream-b and stream-a-2
6. Uninstall stream-a-2 and conduit-b/stream-b/flow-b

During some test runs, it was noticed that after even the last step (6th), the nsm- interfaces were still present in some target pods.

An example of the system during the test run is provided: the nsm-1 interface is stuck in the target pod -ctj6w

[LionelJouin]

It might be the same problem as I have when I try to run the new-attractor-nsm-vlan e2e test: #343

[LionelJouin]

Related to: networkservicemesh/sdk#1434

[LionelJouin]

networkservicemesh/deployments-k8s#8882