Bug 672597

There are a number of places in fence_scsi where the script executes a command via Perl's qx function. Most of these are for executing sg_persist commands. Currently the script does nothing more than:

    $out = qx { $cmd };

    die "[error]: $self\n" if ($?>>8);

If an error occurs executing the command, the script simply dies and reports the name of the subroutine. This can be improved in two ways:

1. Redirect stderr to /dev/null.
2. Log any errors with log_error.

Redirecting stderr to /dev/null keeps some garbage from the sg_persist commands from making its way into the logs. This is a very minor change.

Using log_error instead of simply calling die is preferable since it will write a properly formatted to the logfile.

The improved code would do replace the qx and die calls with:

    $out = qx { $cmd 2> /dev/null };
    $err = ($?>>8);

    if ($err != 0) {
        log_error ("$self (err=$err)");
    }

This code  will correctly write the error to the logfile and include the error code, which might be useful for debugging purposes.