Take in a client list and return dicts with their age and hostname.

def GetClientStates(self, client_list, client_chunk=50):
    """Take in a client list and return dicts with their age and hostname."""
    for client_group in collection.Batch(client_list, client_chunk):
      for fd in aff4.FACTORY.MultiOpen(
          client_group,
          mode="r",
          aff4_type=aff4_grr.VFSGRRClient,
          token=self.token):
        result = {}
        result["age"] = fd.Get(fd.Schema.PING)
        result["hostname"] = fd.Get(fd.Schema.HOSTNAME)
        yield (fd.urn, result)