feature #4206: do not crash getting disk info in poll
feature #4206: do not crash getting disk info in poll

(cherry picked from commit 7d6f91a369cdd31a788d8d44cece531357fa7fb3)

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