fix: ensure temporary IAM role is removed on EC2 dry-run or attach failure

[gnought]

Description

A temporary IAM role is created but not cleaned up when an error occurs while attaching the role to the instance profile.

packer-plugin-amazon/builder/common/step_iam_instance_profile.go

Lines 151 to 159 in 49961be

	_, err = iamsvc.AddRoleToInstanceProfile(&iam.AddRoleToInstanceProfileInput{
	RoleName: roleResp.Role.RoleName,
	InstanceProfileName: profileResp.InstanceProfile.InstanceProfileName,
	})
	if err != nil {
	ui.Error(err.Error())
	state.Put("error", err)
	return multistep.ActionHalt
	}

The same issue also occurs when an error is returned during the EC2 dry-run test.

packer-plugin-amazon/common/step_iam_instance_profile.go

Lines 229 to 234 in 49961be

	if err != nil {
	err := fmt.Errorf("timed out waiting for IAM changes to propagate to EC2: %s", err)
	log.Printf("[DEBUG] %s", err.Error())
	state.Put("error", err)
	return multistep.ActionHalt
	}

The root clause is the code skips setting s.roleIsAttached = true. This PR ensures that the temporary role is properly removed in both failure scenarios.

A excerpt of packer log:

2026/02/16 13:24:11 ui: 2026-02-16T13:24:11+08:00: ==> ubuntu.amazon-ebssurrogate.jammy: Deleting temporary role...
2026/02/16 13:24:11 ui error: 2026-02-16T13:24:11+08:00: ==> ubuntu.amazon-ebssurrogate.jammy: Error operation error IAM: DeleteRole, https response error StatusCode: 409, RequestID: d1062ddd-a4a5-4032-a2ec-6a84c7514b9d, DeleteConflict: Cannot delete entity, must remove roles from instance profile first.. Please delete the role manually: packer-6992a9f0-07ce-f274-22b5-311327335af4
2026/02/16 13:24:11 ui: 2026-02-16T13:24:11+08:00: ==> ubuntu.amazon-ebssurrogate.jammy: Deleting temporary instance profile...
2026/02/16 13:24:12 ui error: 2026-02-16T13:24:12+08:00: ==> ubuntu.amazon-ebssurrogate.jammy: Error operation error IAM: DeleteInstanceProfile, https response error StatusCode: 409, RequestID: d349dd8a-9c8f-48e6-9242-fecbb5e986ae, DeleteConflict: Cannot delete entity, must remove roles from instance profile first.. Please delete the instance profile manually: packer-6992a9f0-07ce-f274-22b5-311327335af4

Resolved Issues

If your PR resolves any open issue(s), please indicate them like this so they will be closed when your PR is merged:

Rollback Plan

If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

No