ofproto: Honour NXFMF_OWN flag of flow monitors

If NXFMF_OWN is not set then full updates should be sent.
Prior to this change an abbreviated update is always sent
to the controller to which a monitor belongs, that is,
the NXFMF_OWN flag is ignored.

I noticed this while working on support for OpenFlow1.4 flow monitors.

Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>