feature #4064: support quiesce for disk snapshots
feature #4064: support quiesce for disk snapshots

(cherry picked from commit 1245c82c1fe24f6c0817a5ca33c7073c0bf80635)

alvarosimon/one,OpenNebula/one,juanmont/one,ohamada/one,abelCoronado93/one,OpenNebula/one,hsanjuan/one,hsanjuan/one,goberle/one,goberle/one,alvarosimon/one,hsanjuan/one,abelCoronado93/one,juanmont/one,atodorov-storpool/one,ohamada/one,ohamada/one,OpenNebula/one,baby-gnu/one,hsanjuan/one,OpenNebula/one,ohamada/one,alvarosimon/one,unistra/one,atodorov-storpool/one,ohamada/one,atodorov-storpool/one,OpenNebula/one,unistra/one,OpenNebula/one,OpenNebula/one,abelCoronado93/one,unistra/one,abelCoronado93/one,abelCoronado93/one,atodorov-storpool/one,atodorov-storpool/one,unistra/one,atodorov-storpool/one,juanmont/one,goberle/one,ohamada/one,alvarosimon/one,baby-gnu/one,atodorov-storpool/one,baby-gnu/one,baby-gnu/one,hsanjuan/one,juanmont/one,ohamada/one,unistra/one,ohamada/one,unistra/one,goberle/one,hsanjuan/one,atodorov-storpool/one,baby-gnu/one,abelCoronado93/one,alvarosimon/one,juanmont/one,OpenNebula/one,abelCoronado93/one,goberle/one,atodorov-storpool/one,baby-gnu/one,hsanjuan/one,juanmont/one,alvarosimon/one,unistra/one,baby-gnu/one,juanmont/one,alvarosimon/one,hsanjuan/one,abelCoronado93/one,goberle/one,OpenNebula/one,juanmont/one,alvarosimon/one,goberle/one,baby-gnu/one,goberle/one,unistra/one,juanmont/one