testing: fix goroutine leak in TestClientUpdatesParamsAfterGoAway (#5024)
testing: fix goroutine leak in TestClientUpdatesParamsAfterGoAway (#5024)


stanley-cheung/grpc-go,dfawley/grpc-go,grpc/grpc-go,grpc/grpc-go,menghanl/grpc-go,stanley-cheung/grpc-go,menghanl/grpc-go,dfawley/grpc-go