Cooja: Fix command line override of ContikiPath

Without the fix the command line parameter was overwritten by the simulation configuration.

tools/cooja/java/se/sics/cooja/GUI.java

@@ -2790,12 +2790,8 @@ public class GUI extends Observable {
    *          New value
    */
   public static void setExternalToolsSetting(String name, String newVal) {
-    if (specifiedContikiPath != null && "PATH_CONTIKI".equals(name)) {
-      specifiedContikiPath = newVal;
-    } else {
     currentExternalToolsSettings.setProperty(name, newVal);
   }
-  }
 
   /**
    * Load external tools settings from default file.