Reverting to a Snapshot
When you revert to a snapshot, you restore a virtual machine to the state it was in when the snapshot was taken. The VirtualMachine.RevertToSnapshot_Task allows you to specify a target host and whether the virtual machine should be powered on.
If the virtual machine was running when the snapshot was taken, and you restore it, you must either specify the host to restore the snapshot to, or set the SupressPowerOn flag to true.