python: Use PyBytes converter for init_lockspace API
    
    This API was deprecated by write_lockspace but we want the
    lockspace/resource name as bytes change to be uniform so we
    modify it as well for sake of old use cases.
    
    Also added stub test for argument parsing.
    
    Implications:
    
    - Py2 : no difference
    - Py3 : if used, only accept bytes for lockspace name.