fix: vsphere-clone: rearrange build steps to ensure source VM exists before deleting target

[YuriyAM]

Summary

This PR addresses an issue in the vsphere-clone builder where using the -force flag can lead to unintentional deletion of the target VM, which may result in the loss of critical data if the target VM is the only copy of a virtual machine.

Issue description

Currently, when the -force flag is specified, the vsphere-clone builder first deletes the target VM before verifying that the source VM to be cloned exists. If the source VM is missing, this process leaves users without a VM to clone and potentially results in data loss.

Use case

In our environment, Packer is used to perform regular updates on legacy virtual machine templates. These templates are unique, lack proper build configurations, and cannot be easily replicated. If, for any reason, human intervention results in running packer build with the -force flag, there is a significant risk of losing irreplaceable data.

Testing

Testing was performed to confirm:

1. Source VM existence is verified before any deletion action on the target VM.
2. With the -force flag, the target VM is only deleted if a source VM exists.

Related issues

• Closes vsphere-clone: Unwanted behavior using -force flag when source virtual machine doesn't exist #490

[hashicorp-cla-app]

All committers have signed the CLA.

[tenthirtyam]

Could you please link this pull request to an issue?

[YuriyAM]

@tenthirtyam I couldn’t find any open or closed issue that this merge request directly relates to. If it’s required by your procedures, I’d be happy to create one 😊

[tenthirtyam]

yes, please. This is mentioned in the contributed guidelines. 😉

[YuriyAM]

I might have overlooked that 😅 Thanks for guiding me! Here’s the link to the issue—#490