public static byte[] padTail(final byte[] a, final int length) {
    byte[] padding = new byte[length];
    for (int i = 0; i < length; i++) {
      padding[i] = 0;
    }
    return add(a, padding);
  }
Make a new byte array from a subset of bytes at the tail of another, zero padded as desired.
@param a      array
@param length new array size
@return Value in <code>a</code> plus <code>length</code> appended 0 bytes
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Bytes.java