Add 'sessionId' into privet/info Current implementation is a Unix timestamp plus counter. BUG=26140026 Change-Id: Idfe0aa81c49e6dab5d638cbedfbeb460b70b5864 Reviewed-on: https://weave-review.googlesource.com/2010 Reviewed-by: Alex Vakulenko <avakulenko@google.com>