fix: return security group id for docker-autoscaler in runner_sg_id (#1249)

## Description

For the `docker-autoscaler` workers the security group id was not
returned, which is added by this PR. According to the description of the
variable, we can expect it for every worker type creating separate
instances.

Fixes #1241

Author: kayman-mk

outputs.tf

@@ -39,8 +39,8 @@ output "runner_agent_sg_id" {
 }
 
 output "runner_sg_id" {
-  description = "ID of the security group attached to the docker machine runners."
-  value       = length(aws_security_group.docker_machine) > 0 ? aws_security_group.docker_machine[0].id : null
+  description = "ID of the security group attached to the worker instances (docker machine/autoscaler runners)."
+  value       = var.runner_worker.type == "docker-autoscaler" ? aws_security_group.docker_autoscaler[0].id : (var.runner_worker.type == "docker+machine" ? aws_security_group.docker_machine[0].id : null)
 }
 
 output "runner_eip" {