Previously, imported data would never be deleted. As
nodes/services/checks were registered and deregistered, resources
deleted from the exporting cluster would accumulate in the imported
cluster.
This commit makes updates to replication so that whenever an update is
received for a service name we reconcile what was present in the catalog
against what was received.
This handleUpdateService method can handle both updates and deletions.
Require use of mesh gateways in order for service mesh data plane
traffic to flow between peers.
This also adds plumbing for envoy integration tests involving peers, and
one starter peering test.
Freddy