ofproto-dpif: Don't slow-path controller actions.

ofproto-dpif: Don't slow-path controller actions.

Controller actions have become more commonly used for purposes other
than just making forwarding decisions (e.g., packet logging).  A packet
that needs to be copied to the controller and forwarded would always be
sent to ovs-vswitchd to be handled, which could negatively affect
performance and cause heavier CPU utilization in ovs-vswitchd.

This commit changes the behavior so that OpenFlow controller actions
become userspace datapath actions while continuing to let packet
forwarding and manipulation continue to be handled by the datapath
directly.

This patch still slow-paths controller actions with the "pause" flag
set.  A future patch will stop slow-pathing these pause actions as
well.

Signed-off-by: Justin Pettit <jpettit@ovn.org>
Acked-by: Ben Pfaff <blp@ovn.org>