(POOLER-40) Do not return folders with get_pool_vms

This commit updates get_pool_vms to only return if the object is a VirtualMachine. Without this change a folder wtihin a VM target folder can be discovered and destroyed as though it were a VM.

lib/vmpooler/providers/vsphere.rb

@@ -52,7 +52,7 @@ module Vmpooler
             return vms if folder_object.nil?
 
             folder_object.childEntity.each do |vm|
-              vms << { 'name' => vm.name }
+              vms << { 'name' => vm.name } if vm.is_a? RbVmomi::VIM::VirtualMachine
             end
           end
           vms