Set the clock format, either 12h or 24h format.

    CLI Example:

    .. code-block:: bash

        salt '*' gnome.setClockFormat <12h|24h> user=<username>

def setClockFormat(clockFormat, **kwargs):
    '''
    Set the clock format, either 12h or 24h format.

    CLI Example:

    .. code-block:: bash

        salt '*' gnome.setClockFormat <12h|24h> user=<username>

    '''
    if clockFormat != '12h' and clockFormat != '24h':
        return False
    _gsession = _GSettings(user=kwargs.get('user'),
                           schema='org.gnome.desktop.interface',
                           key='clock-format')
    return _gsession._set(clockFormat)