nfs: fix write in embedded client

Motivation:
as oncrpc4j have changed Xdr#xdrEncodeByteBuffer to not flip provided
buffer we should not set write buffer position to the buffer's limit to
allow data to be read.

Modification:
do not set buffers position to limit as Buffer#remaining will return
zero.

Result:
embedded nfs4 client able to write.

Acked-by: Albert Rossi
Target: master, 0.17

core/src/main/java/org/dcache/nfs/v4/client/CompoundBuilder.java

@@ -321,7 +321,6 @@ public CompoundBuilder withRemove(String path) {
 
     public CompoundBuilder withWrite(long offset, byte[] data, stateid4 stateid) {
         ByteBuffer buf = ByteBuffer.wrap(data);
-        buf.position(data.length);
         return withWrite(offset, buf, stateid);
     }