Removed placement_group from outputs

Author: antonbabenko

outputs.tf

@@ -8,10 +8,11 @@ output "availability_zone" {
  value = ["${aws_instance.this.*.availability_zone}"]
 }
 
-output "placement_group" {
- description = "List of placement groups of instances"
- value = ["${aws_instance.this.*.placement_group}"]
-}
+// GH issue: https://github.com/terraform-aws-modules/terraform-aws-ec2-instance/issues/8
+//output "placement_group" {
+// description = "List of placement groups of instances"
+// value = ["${element(concat(aws_instance.this.*.placement_group, list("")), 0)}"]
+//}
 
 output "key_name" {
  description = "List of key names of instances"