make sure that the path for the payload droplet is uniquie, @peda

src/Nloc.java

@@ -126,12 +126,17 @@ public class Nloc {
   }
 
   public List<Channel> getDesiredPath(List<Channel> modules,
-      List<List<Channel>> pathlist) {
+      List<List<Channel>> pathlist) throws NlocStructureException {
     List<Channel> found = new ArrayList<Channel>();
     for (List<Channel> path : pathlist) {
-      if (path.containsAll(modules)) {
+      if (path.containsAll(modules) && found.isEmpty()) {
         found = path;
-      }
+      } else if (path.containsAll(modules) && !found.isEmpty()) {
+        throw new NlocStructureException("Paths are not unique!");
+      } 
+    }
+    if (found.isEmpty()) {
+      throw new NlocStructureException("No path found that covers all given Modules");
     }
     return found;
   }