ofproto: Specialize ofproto_send_packet() for uses the callers really want.

ofproto: Specialize ofproto_send_packet() for uses the callers really want.

The callers of ofproto_send_packet() actually just want to send a packet
out on a port, possibly tagged with a VLAN, but the interface forced them
to compose a set of OpenFlow actions, which made it harder to use than
necessary.  This commit specializes the interface for the purposes that
the callers really wanted, making it easier to use.

handle_miss_upcall() can now take advantage of this function, too.