fix deleting qcow2 images (#123)
fix deleting qcow2 images (#123)

following this forum thread

https://forum.opennebula.org/t/opennebula-5-0-2-attach-detach-images-datastore-folder-not-cleaned-up/3111
OpenNebula/one,goberle/one,abelCoronado93/one,goberle/one,baby-gnu/one,atodorov-storpool/one,abelCoronado93/one,OpenNebula/one,abelCoronado93/one,unistra/one,baby-gnu/one,OpenNebula/one,OpenNebula/one,unistra/one,goberle/one,juanmont/one,abelCoronado93/one,ohamada/one,juanmont/one,atodorov-storpool/one,juanmont/one,OpenNebula/one,OpenNebula/one,ohamada/one,juanmont/one,OpenNebula/one,juanmont/one,atodorov-storpool/one,unistra/one,ohamada/one,juanmont/one,atodorov-storpool/one,unistra/one,goberle/one,baby-gnu/one,baby-gnu/one,juanmont/one,ohamada/one,goberle/one,goberle/one,abelCoronado93/one,unistra/one,juanmont/one,atodorov-storpool/one,ohamada/one,OpenNebula/one,ohamada/one,atodorov-storpool/one,ohamada/one,OpenNebula/one,baby-gnu/one,ohamada/one,atodorov-storpool/one,atodorov-storpool/one,goberle/one,abelCoronado93/one,baby-gnu/one,atodorov-storpool/one,abelCoronado93/one,baby-gnu/one,unistra/one,baby-gnu/one,abelCoronado93/one,unistra/one,goberle/one,juanmont/one,unistra/one