This is a fix on top of #220. The previous change relied on the management agent's presence, but we actually want to know if the VM has PV drivers available.
Testing
[x] TestAccXenorchestraVm_diskAndNetworkAttachmentIgnoredWhenHalted passes when it would fail prior to this improved graceful shutdown behavior
[x] Verified that this is an accurate means of detecting PV drivers are available. Used the VM below as a reference.
This is a fix on top of #220. The previous change relied on the management agent's presence, but we actually want to know if the VM has PV drivers available.
Testing
TestAccXenorchestraVm_diskAndNetworkAttachmentIgnoredWhenHaltedpasses when it would fail prior to this improved graceful shutdown behavior