Fix regression from 40f956b. Invalid length parameter. (#322)

Also Fixes #306

Author: dkocher

src/main/java/net/schmizz/sshj/connection/channel/ChannelOutputStream.java

@@ -138,7 +138,7 @@ public synchronized void write(final byte[] data, int off, int len)
         int length = len;
         int offset = off;
         while (length > 0) {
-            final int n = buffer.write(data, offset, len);
+            final int n = buffer.write(data, offset, length);
             offset += n;
             length -= n;
         }