Function to allow non-fileserver functions to clear update locks

    clear_func
        A function reference. This function will be run (with the ``remote``
        param as an argument) to clear the lock, and must return a 2-tuple of
        lists, one containing messages describing successfully cleared locks,
        and one containing messages describing errors encountered.

    role
        What type of lock is being cleared (gitfs, git_pillar, etc.). Used
        solely for logging purposes.

    remote
        Optional string which should be used in ``func`` to pattern match so
        that a subset of remotes can be targeted.

    lock_type : update
        Which type of lock to clear

    Returns the return data from ``clear_func``.

def clear_lock(clear_func, role, remote=None, lock_type='update'):
    '''
    Function to allow non-fileserver functions to clear update locks

    clear_func
        A function reference. This function will be run (with the ``remote``
        param as an argument) to clear the lock, and must return a 2-tuple of
        lists, one containing messages describing successfully cleared locks,
        and one containing messages describing errors encountered.

    role
        What type of lock is being cleared (gitfs, git_pillar, etc.). Used
        solely for logging purposes.

    remote
        Optional string which should be used in ``func`` to pattern match so
        that a subset of remotes can be targeted.

    lock_type : update
        Which type of lock to clear

    Returns the return data from ``clear_func``.
    '''
    msg = 'Clearing {0} lock for {1} remotes'.format(lock_type, role)
    if remote:
        msg += ' matching {0}'.format(remote)
    log.debug(msg)
    return clear_func(remote=remote, lock_type=lock_type)