Modified VMware mgmt_system

list_vm() method used the api call get_registered_vms() which on the
surface appeared to give correct results. However, it returned
path+vmx_filename which in some cases differs from the vm_names.

The fix now pulls from an attribute set instead and is able to tell the
difference between templates and non-templates.
Merge pull request #199 from psav/fix_vmware_list_vm

Modified VMware mgmt_system