Vcloud director/miscellany of improvments

Hi @geemus and @nosborn,

This PR is a set miscellany of small improvements for vcloud director:
- using post_undeploy_vapp
- power_off for a vm
- when a vapp is created successfully returns the vapp-id
- shutdown method was duplicate
- ready? method implemented
- accessing to the parent vapp even if the vm is orphan (query result)
- memory is an integer

Thanks,

Rodrigo