ofproto-dpif: Accept OpenFlow-like flows in "ofproto/trace".
Until now it has not been possible to directly trace flows that include
register values and other concepts that are not in datapath flows, because
"ofproto/trace" requires a flow in the format output by "ovs-dpctl
dump-flows", which doesn't know anything about registers. This commit
makes it possible to instead specify an OpenFlow-like flow.
Feature #10084.
Requested-by: Igor Ganichev <iganichev@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>