Flaky test suite extras

[zasweq]

I've seen this a few times now.

It cannot determine that the server started in Load Balancing Example:

 testing: features/load_balancing 
 successfully built server 
 waiting for server to start 
 cannot determine if server started 

https://github.com/zasweq/grpc-go/actions/runs/11043178342/job/30676993270

[arjan-bal]

https://github.com/grpc/grpc-go/actions/runs/11812153731/job/32906871665