read .tfstate file
        :param file_path: relative path to working dir
        :return: states file in dict type

def read_state_file(self, file_path=None):
        """
        read .tfstate file
        :param file_path: relative path to working dir
        :return: states file in dict type
        """

        working_dir = self.working_dir or ''

        file_path = file_path or self.state or ''

        if not file_path:
            backend_path = os.path.join(file_path, '.terraform',
                                        'terraform.tfstate')

            if os.path.exists(os.path.join(working_dir, backend_path)):
                file_path = backend_path
            else:
                file_path = os.path.join(file_path, 'terraform.tfstate')

        file_path = os.path.join(working_dir, file_path)

        self.tfstate = Tfstate.load_file(file_path)