BUG-1297 + BUG-1277 Reflection of OFJava's ByteBufUtils move on OFPlugin

Merge only after these two are merged :

https://git.opendaylight.org/gerrit/#/c/8552/
https://git.opendaylight.org/gerrit/#/c/8554/
https://git.opendaylight.org/gerrit/#/c/8609/

BUG-1297 flowCookie with null value (unit test blocker)

- added if-branch in order not to create flowCookie if null input

Change-Id: Ib4149f9f41a6b3b2b7b84ec6713d83391db598a9
Signed-off-by: Martin Bobak <mbobak@cisco.com>
Signed-off-by: Michal Rehak <mirehak@cisco.com>