Update S2681: Fix FP on try-catch block

[jccollet]

The following code triggers rule S2681 (Multiline blocks should be enclosed in curly braces) on the 'try {' line. Obviously a FP.
See Issue on peach

using System;

namespace MyLibrary {
    public class MyClass {
        internal static void ReadBytesAsync (
            this Stream stream, int length, Action<byte[]> completed, Action<Exception> error) {
            var buffer = new byte[length];
            stream.BeginRead (
                buffer,
                0,
                length,
                ar => {
                    try {
                        var len = stream.EndRead (ar);
                        var bytes = len < 1 ?
                            new byte[0] :
                            len < length ?
                            stream.readBytes (buffer, len, length - len) :
                            buffer;
                        if (completed != null)
                            completed (bytes);
                    } catch (Exception ex) {
                        if (error != null)
                            error (ex);
                    }
                },
                null);
        }
    }
}

[valhristov]

Duplicates #264