Get the short os name from the OS name OID string.

def get_system_name(self, oid_system_name):
        """Get the short os name from the OS name OID string."""
        short_system_name = None

        if oid_system_name == '':
            return short_system_name

        # Find the short name in the oid_to_short_os_name dict
        for r, v in iteritems(oid_to_short_system_name):
            if re.search(r, oid_system_name):
                short_system_name = v
                break

        return short_system_name