[vSphere] Implementation of feature to specify scsi_controller type at create time

This feature is an implementation for creating virtual machines with a userdefined storage controller on bases of the Vsphere VirtualSCSIController.
If you don't pass a userdefined storage controller the VirtualLsiLogicController will be used (as before).
If you want to specify the storage controller by userself do it as follows:
```
vm=compute.servers.create(
   "name" => "..", 
   "cluster" => compute.datacenters.first.clusters.first.name, 
   "datacenter" => compute.datacenters.first.name, 
   "memory_mb"=>1024, 
   "cpus"=>2, 
   "guest_id"=>"rhel6_64Guest", 
   "scsi_controller" => { "type" => "ParaVirtualSCSIController", "shared" => true }, 
   "interfaces"=>[interface,], 
   "volumes"=>[volume]
)
```