dlm_controld: fix -Wstringop-truncation warnings
    
    This patch fixes in dlm_controld all -Wstringop-truncation warnings.
    There exists two different cases inside the code:
    
    1. string buffer without null termination:
    
    Code work as expected in this case a pragma is introduced to ignore the
    warning.
    
    2. string buffer with null termination:
    
    The function strncpy() will not leave the destination buffer with a null
    termination symbol if the buffer doesn't fit. That's why gcc above 8.0
    print warnings. Obviously there are some memset() to zero the buffer and
    doing a strncpy() minus one of the buffer length afterwards which seems
    fine. The fact that gcc still complains and knowing other discussions
    about memset() I believe that there might be reasons why gcc doesn't
    stop to complain about such code or gcc isn't able to detect it.
    
    However this patch will guarantee that the destination buffer is always
    null terminated and the full destination buffer size is used now.