Enhancement: treat session lock error from VBoxManage as a signal that the VM is already running

_This issue was originally opened by @mcandre as hashicorp/packer#9334. It was migrated here as a result of the [Packer plugin split](https://github.com/hashicorp/packer/issues/8610#issuecomment-770034737). The original body of the issue is below._

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#### Feature Description

Please treat session lock error from VBoxManage as a signal that the VM is already running. That could help packer integrate better with the hypervisor and assess VM state more accurately.