Update HDD stats using the input method.

def update(self):
        """Update HDD stats using the input method."""
        # Init new stats
        stats = self.get_init_value()

        if self.input_method == 'local':
            # Update stats using the standard system lib
            stats = self.glancesgrabhddtemp.get()

        else:
            # Update stats using SNMP
            # Not available for the moment
            pass

        # Update the stats
        self.stats = stats

        return self.stats