make the install_node.sh more robust
make the install_node.sh more robust

mapnik/node-mapnik,mapnik/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,tomhughes/node-mapnik,langateam/node-mapnik,langateam/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,langateam/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,langateam/node-mapnik,mapnik/node-mapnik,CartoDB/node-mapnik,tomhughes/node-mapnik,CartoDB/node-mapnik,CartoDB/node-mapnik,langateam/node-mapnik,tomhughes/node-mapnik