Make nodes option working again for generate_cluster_xml.py
Make nodes option working again for generate_cluster_xml.py

Option -n or --nodes is broken since d2452a971e5691f3f9712826d333050180282695 when the
input file check was added.

arunthirupathi/voldemort,voldemort/voldemort,FelixGV/voldemort,FelixGV/voldemort,jalkjaer/voldemort,bitti/voldemort,bitti/voldemort,voldemort/voldemort,FelixGV/voldemort,voldemort/voldemort,bitti/voldemort,arunthirupathi/voldemort,FelixGV/voldemort,jalkjaer/voldemort,FelixGV/voldemort,bitti/voldemort,voldemort/voldemort,FelixGV/voldemort,arunthirupathi/voldemort,bitti/voldemort,jalkjaer/voldemort,voldemort/voldemort,arunthirupathi/voldemort,voldemort/voldemort,jalkjaer/voldemort,arunthirupathi/voldemort,arunthirupathi/voldemort,jalkjaer/voldemort,jalkjaer/voldemort,jalkjaer/voldemort,bitti/voldemort,voldemort/voldemort,arunthirupathi/voldemort,FelixGV/voldemort,bitti/voldemort