Check if a server:port combination is a member of a servicegroup

    CLI Example:

    .. code-block:: bash

        salt '*' netscaler.servicegroup_server_exists 'serviceGroupName' 'serverName' 'serverPort'

def servicegroup_server_exists(sg_name, s_name, s_port=None, **connection_args):
    '''
    Check if a server:port combination is a member of a servicegroup

    CLI Example:

    .. code-block:: bash

        salt '*' netscaler.servicegroup_server_exists 'serviceGroupName' 'serverName' 'serverPort'
    '''
    return _servicegroup_get_server(sg_name, s_name, s_port, **connection_args) is not None