Change health check from TCP to HTTPS (#6487)

I kept seeing `TLS handshake error from 10.250.250.158:63770: EOF` from two IP addresses that correlate to my ELB. Changing the health check from TCP to HTTPS stopped the errors from being generated.

contrib/terraform/aws/modules/elb/main.tf

@@ -42,7 +42,7 @@ resource "aws_elb" "aws-elb-api" {
     healthy_threshold   = 2
     unhealthy_threshold = 2
     timeout             = 3
-    target              = "TCP:${var.k8s_secure_api_port}"
+    target              = "HTTPS:${var.k8s_secure_api_port}/healthz"
     interval            = 30
   }