feature #1617: Add default to disk_attribute
feature #1617: Add default to disk_attribute

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