Update a key with a value in the minion datastore

    CLI Example:

    .. code-block:: bash

        salt '*' data.update <key> <value>

def update(key, value):
    '''
    Update a key with a value in the minion datastore

    CLI Example:

    .. code-block:: bash

        salt '*' data.update <key> <value>
    '''
    store = load()
    store[key] = value
    dump(store)
    return True