ofproto: Send port status message for port-mods, right away.

Until now, when it processes OFPT_PORT_MOD message, Open vSwitch has waited
for ports to notify it that their status has changed before it sends a
port status update to controllers.

Also, Open vSwitch never sent port config updates at all for port
modifications other than OFPPC_PORT_DOWN.  I guess that this is a relic
from the era when there was only one controller, since presumably the
controller already knew that it changed the port configuration.  But in the
multi-controller world, it makes sense to send such port status updates,
and I couldn't quickly find anything in OF1.3 or OF1.4 that said they
shouldn't be sent.

EXT-338.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Reported-by: Kmindg G <kmindg@gmail.com>