fix: only create the secrets manager auth policy if user passes a val…

…ue for `existing_secrets_manager_instance_crn` regardless of the value of `skip_cos_sm_auth_policy` (#709)

solutions/instance/main.tf

@@ -17,7 +17,7 @@ module "cos" {
 }
 
 resource "ibm_iam_authorization_policy" "secrets_manager_key_manager" {
-  count                       = var.skip_cos_sm_auth_policy ? 0 : 1
+  count                       = var.skip_cos_sm_auth_policy || var.existing_secrets_manager_instance_crn == null ? 0 : 1
   depends_on                  = [module.cos]
   source_service_name         = "secrets-manager"
   source_resource_instance_id = local.existing_secrets_manager_instance_guid