Fixed length bug in putString (Fixes #187)

Author: hierynomus

src/main/java/net/schmizz/sshj/common/Buffer.java

@@ -246,7 +246,7 @@ public T putBytes(byte[] b) {
      * @return this
      */
     public T putBytes(byte[] b, int off, int len) {
-        return putUInt32(len - off).putRawBytes(b, off, len);
+        return putUInt32(len).putRawBytes(b, off, len);
     }
 
     public void readRawBytes(byte[] buf)

src/main/java/net/schmizz/sshj/sftp/RemoteFile.java

@@ -82,9 +82,7 @@ protected Promise<Response, SFTPException> asyncWrite(long fileOffset, byte[] da
             throws IOException {
         return requester.request(newRequest(PacketType.WRITE)
                 .putUInt64(fileOffset)
-                // TODO The SFTP spec claims this field is unneeded...? See #187
-                .putUInt32(len)
-                .putRawBytes(data, off, len)
+                .putString(data, off, len)
         );
     }