dlm_controld: init plocks_data to zero
    
    Inits plocks_data to zero in case of send_all_plocks_data() does not set
    plocks_data to any value or nodes_added() returns false. This patch fixes
    cppcheck warning:
    
    cpg.c:1299:27: error: Uninitialized variable: plocks_data [uninitvar]
     send_plocks_done(ls, cg, plocks_data);