code: protected File findFeatureManifest() throws IOException {
          for (File root : CustomUtils.listExtensionDirectories()) {
              File[] files = CustomUtils.listFiles(new File(root, FEATURE_DIR));
              if (files != null) {
                  for (File file : files) {
                      if (CustomUtils.isFile(file) && file.getName().toLowerCase().endsWith(MANIFEST_EXT)) {
                          List<String> fileLocations = getFileLocationsFromSubsystemContent(getSubsystemContent(file));
                          for (String fileLocation : fileLocations) {
                              for (File jarRoot : CustomUtils.listRootAndExtensionDirectories()) {
                                  if (getCanonicalPath(jarRoot, fileLocation).equals(extensionJarLocation)) {
                                      return file;
                                  }
                              }
                          }
                      }
                  }
              }
          }
          return null;
      }
docs: find the feature manifest file which contains the location of the extension manifest
  file as Subsystem-Content.
  the directories which are searched are: wlp/user/extensions/lib/features and all
  of the product extension directories.
  
  @throws IOException