BUG-709 packetIn and connectionCookie

- started sending connectionCookie up to MD-SAL wrapped in packetIn
- started honoring connectionCookie coming down from MD-SAL
  wrapped in TransmitPacketInput
- fixed NPE when auxiliary identifier missing

Change-Id: I1f3d1e4392cc8e3b766c4f90ac251e1692ba37eb
Signed-off-by: Michal Rehak <mirehak@cisco.com>