Fixes bug #518
Fixes bug #518

onError() now checks if the error message is empty and warn the user that the server is not reachable.

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