Update apt_ubuntu to display integers instead of floats

plugins/ubuntu/apt_ubuntu

@@ -77,6 +77,7 @@ def config():
     print('graph_category security')
     print('graph_title %s' % (title))
     print('graph_vlabel %s' % (vlabel))
+    print('graph_printf %.0lf')
     for i, archive in enumerate(archives + [other]):
         if len(colour) > i:
             print('%s.colour %s' % (archive, colour[i]))