bug #3559: Set free_mb = 0 when limit > used
bug #3559: Set free_mb = 0 when limit > used

(cherry picked from commit bd45b9776a75b24257d8cd2339d7027e6fdb8850)

atodorov-storpool/one,ggalancs/one,juanmont/one,cloudweavers/one,atodorov-storpool/one,goberle/one,atodorov-storpool/one,cloudweavers/one,spirit03/one,ggalancs/one,alvarosimon/one,spirit03/one,goberle/one,spirit03/one,alvarosimon/one,mattthias/one,unistra/one,juanmont/one,abelCoronado93/one,mattthias/one,OpenNebula/one,goberle/one,baby-gnu/one,tuxmea/one,juanmont/one,fasrc/one,OpenNebula/one,unistra/one,atodorov-storpool/one,alvarosimon/one,ggalancs/one,ohamada/one,goberle/one,hsanjuan/one,fasrc/one,OpenNebula/one,juanmont/one,hsanjuan/one,mattthias/one,unistra/one,ohamada/one,baby-gnu/one,juanmont/one,atodorov-storpool/one,OpenNebula/one,unistra/one,atodorov-storpool/one,mattthias/one,cloudweavers/one,ggalancs/one,mattthias/one,tuxmea/one,spirit03/one,OpenNebula/one,fasrc/one,hsanjuan/one,unistra/one,goberle/one,juanmont/one,goberle/one,spirit03/one,mattthias/one,ohamada/one,mattthias/one,unistra/one,fasrc/one,hsanjuan/one,fasrc/one,tuxmea/one,fasrc/one,abelCoronado93/one,baby-gnu/one,ohamada/one,tuxmea/one,tuxmea/one,hsanjuan/one,fasrc/one,abelCoronado93/one,goberle/one,abelCoronado93/one,ggalancs/one,unistra/one,juanmont/one,atodorov-storpool/one,ggalancs/one,cloudweavers/one,alvarosimon/one,baby-gnu/one,ohamada/one,abelCoronado93/one,unistra/one,abelCoronado93/one,alvarosimon/one,cloudweavers/one,spirit03/one,ohamada/one,baby-gnu/one,goberle/one,alvarosimon/one,alvarosimon/one,abelCoronado93/one,OpenNebula/one,cloudweavers/one,tuxmea/one,atodorov-storpool/one,cloudweavers/one,tuxmea/one,abelCoronado93/one,mattthias/one,hsanjuan/one,cloudweavers/one,baby-gnu/one,baby-gnu/one,spirit03/one,ggalancs/one,juanmont/one,atodorov-storpool/one,alvarosimon/one,OpenNebula/one,baby-gnu/one,tuxmea/one,ohamada/one,fasrc/one,OpenNebula/one,OpenNebula/one,spirit03/one,ggalancs/one,ohamada/one,hsanjuan/one,hsanjuan/one,juanmont/one