Normalize sanlock exit code
    
    Normalize sanlock exit code, so it exit with EXIT_FAILURE on all
    failures.
    
    Previously sanlock terminated with exit code 255 if lockfile() failed,
    145 if client cannot connect to the daemon, or any other number
    depending on return value of failing function.
    
    Exit codes above 128 should be returned only when the process was
    terminated by signal (typically 128 + signo), and using them for other
    errors may confuse applications managing sanlock.
    
    Since sanlock exit code is not documented, this change should not break
    any user code.
    
    Signed-off-by: Nir Soffer <nsoffer@redhat.com>