BUG-1952 Flow update rpc

- in case that delete and recreate of flow is required then
  the action after delete should be add -> was modify
- fixed xid propagation to notification
- using RpcResultBuilder

Change-Id: Idd519256519e32b2cd475b4cd954fe16f7518e66
Signed-off-by: Michal Rehak <mirehak@cisco.com>
Merge "BUG-1952 Flow update rpc"