Bug 1985 - NPE when running groupbasedpolicy POC demo

- OFSessionUtild doesn't set session as valid anymore, session
  management moved to SessionManagerOFImpl
- session validation/invalidation is synchronized
- when registration is about to be closed SalRegistrationManager checks
  whether session from which registration is originated is valid

Change-Id: I2c523586676d3533aaf84afd2cecc38bd53181f4
Signed-off-by: Martin Bobak <mbobak@cisco.com>
BUG-1997: moving barrier after message

- before <message>.isBarrier rendered into barrier exchange before message
  now barrier exchange occurs after message

Change-Id: I1e4c4738eedef50b737a2d395123873156740df6
Signed-off-by: Michal Rehak <mirehak@cisco.com>
BUG-1626: low cbench performance against dataStore

- replaced constant flow.id with incremented value

Change-Id: Iae146611d54782805260c8341504ac6661213dc8
Signed-off-by: Michal Rehak <mirehak@cisco.com>
Merge "BUG-1997: moving barrier after message"
Merge "BUG-1626: low cbench performance against dataStore"