@Override
  public boolean isSendComplete() {
    return sizeInBytes() == sentBytes;
  }
Override release even if the {@link #content()}'s result is not null. When the {@link #prepareBuffer()} is
not invoked, there will be {@link #blob} and {@link #crcByteBuf} created but not returned by {@link #content()},
and we have to release them.
@return
ambry-protocol/src/main/java/com/github/ambry/protocol/PutRequest.java