public List<Module> getModules(Long mpackId) {
    Mpack mpack = mpackMap.get(mpackId);
    return mpack.getModules();
  }
Fetches the mpack info stored in the memory for mpacks/{mpack_id} call.

@param mpackId
@return list of {@link Module}
ambari-server/src/main/java/org/apache/ambari/server/mpack/MpackManager.java