Teleport agent can't discover all proxies on AWS

In case if teleport is deployed on AWS in IOT mode or Trusted clusters are being used, one can observe the following repeated logs:

Connected to <host>:443 target:example.com:443 reversetunnel/agent.go:343
INFO [PROXY:AGE] Outbound tunnel stats. stats:map[connecting:0 discovering:1 connected:1 discovered:0 disconnected:0] target:memory cluster:memory reversetunnel/agentpool.go:432

Notice the discovering section here. It means that agent constantly tries to connect (discover) both proxies behind the load balancer. Debug logs will show the following picture:

DEBU [PROXY:AGE] Missed, connected to [ip-1-us-west-2-compute-internal.memory 1-us-west-2-compute-internal example.com] instead of ip-2-us-west-2-compute-internal. target:example.com:443 reversetunnel/agent.go:364
DEBU [PROXY:AGE] Changing state discovering -> disconnected. target:example.com:443 reversetunnel/agent.go:202

The following is fixed by turning on cross zone load balancing on the load balancer settings.